It's back to school time in the NFL as players are now reporting back to their teams after the summer break for the start of training camp. As is the case in some years, however, there are a handful of stars who decide against reporting and instead are holding out, which is largely due to contractual issues the player has with his respective team. 

This year is no different in that regard as there are a handful of players in 2023 who are staying away from their teams until their contract situation is cleared up. That includes heavy hitters like running back Josh Jacobs, and defensive lineman Chris Jones. Saquon Barkley and the Giants agreed to a new one-year deal to avoid the back from holding out. These disputes are largely still in their infancy and all sides are likely hoping to reach a resolution so that things don't devolve into more toxic situations like we've seen in the past. 

Below, you'll find the top 12 ugliest holdouts in league history, and what these current stars could be facing. 

12. John Hannah, Patriots (1977)

At the advice of his agent, Hannah, New England's Hall of Fame offensive lineman, sat out the first three games of the 1977 season over a contract dispute. So did Hannah's teammate, fellow lineman Leon Gray (who had the same agent as Hannah). 

Hannah eventually returned to the Patriots after signing his new deal. While the '77 season was a disappointing one for both himself and the Patriots, Hannah would play eight more seasons in New England after his holdout-shortened season. Over that span, Hannah earned eight Pro Bowl and six All-Pro selections while helping the Patriots advance to their first-ever Super Bowl at the end of the 1985 season. 

11. Earl Thomas, Seahawks (2018)

Thomas serves as a cautionary tale for current-day players with regard to playing without a longterm contract. After missing Seattle's entire 2018 training camp after failing to come to terms with the team on a longterm contract, Thomas, a six-time Pro Bowler, four-time All-Pro and valuable member of Seattle's championship defense of 2013, returned just before the start of the regular season. 

Thomas would sustain a broken bone in his left leg during the fourth game of the season, thus ending his season and potentially crippling his value on the 2019 free-agent market. Thomas didn't hide his anger upon sustaining the injury, flipping the middle finger to the Seahawks' sideline as he was carted off the field. 

Despite the injury, Thomas did ink a four-year, $55 million contract with the Ravens this past offseason that includes $32 million guaranteed. 

10. Darrelle Revis, Jets (2010)

Revis' holdout will be remembered by anyone who watched the situation play out in real-time on HBO's "Hard Knocks," which covered the Jets training camp in the summer of 2010. Revis was a standout cornerback who was coming off his first All-Pro season. The Jets, under rookie head coach Rex Ryan, were coming off a surprise run to the AFC title game. 

Revis' representatives and the Jets' brass initially failed to come to terms on a new deal, which led Revis to sit out the majority of New York's training camp. With pressure mounting and "Hard Knocks" watching his every move, a frustrated Ryan drove to Jets owner Woody Johnson's home to help settle the issue. 

Shortly after Ryan's meeting with Johnson, Revis was given a four-year, $32 million deal. Revis returned to the team a week before the start of the regular season, helping New York make a return trip to the AFC title game. 

9. Emmitt Smith, Cowboys (1993)

Smith felt that he was in line for a big payday after becoming the first rushing champion to win the Super Bowl. Smith's boss, Cowboys owner Jerry Jones, initially bulked at giving Smith his lucrative new contract, resulting in Smith sitting out the entire 1993 training camp. 

Smith's absence continued into the regular season, as Dallas stumbled to an 0-2 start that included a home loss to the Bills, the team that the Cowboys had dismantled in the Super Bowl eight months earlier. Dallas' disastrous start forced a resigned Jones to give Smith his payday. Smith responded by earning All-Pro honors that season while leading the Cowboys to a 12-2 finish to the regular season. 

Smith wasn't done there, earning MVP honors in Super Bowl XXVIII as Dallas whipped Buffalo for a second-straight year. Trailing at halftime, the Cowboys doubled-down on their use of Smith, who finished the game with 132 yards and two second-half touchdowns in a 30-13 Dallas victory. 

In the end, Jones got his ring, and Emmitt got his money. Both men currently reside in the Pro Football Hall of Fame. 

8. Fred Dean, 49ers (1984)

The Hall of Fame defense end had not one but three contentious contract situations during his decorated career. 

Traded to San Francisco following a contract dispute in San Diego in 1981, Dean earned All-Pro honors that season while helping the 49ers win their first of four Super Bowl titles during the decade. 

After recording 17 sacks (that included a then single-game record 6 sacks) during the 1983 season, Dean, on the books to make $250,000 that season, wanted a one-year salary of $800,000 entering the 1984 season. After San Francisco decided against giving him the big bonus (they had another contract situation with another future Hall of Famer, Ronnie Lott, to deal with), Dean opted to skip the first 10 games of the season. 

Dean made an impact after ending his holdout, recording four sacks in five games while helping the 49ers become the first team in league history to win 15 regular-season games. In three postseason games, Dean recorded a whopping four sacks while helping spearhead San Francisco's run to a second Super Bowl title in a four-year span. In all, Dean recorded seven sacks in eight games with the '84 49ers despite not starting in a single game. He played out his contract with San Francisco in 1985, recording just three sacks in 16 games without getting a single start. He retired following the season and was inducted into the Pro Football Hall of Fame in 2008.

7. Cornelius Bennett, Colts (1987)

The second-overall pick in the 1987 draft, Bennett, an outside linebacker out of Alabama, held out for 102 days after he and the Colts could not come to terms on his rookie contract. 

At the conclusion of that year's players' strike, Indianapolis included Bennett in a three-team trade that included sending Bennett to Buffalo while receiving All-Pro running back Eric Dickerson from the Rams. While Indianapolis and Dickerson enjoyed some fruitful seasons together, Bennett and the Bills were the clear winners in this transaction. In nine seasons in Buffalo, Bennett earned five Pro Bowl selections while helping the Bills become the first team in NFL history to appear in four consecutive Super Bowls.

Ironically, Bennett ended his career with the Colts, enjoying two productive seasons in Indianapolis before retiring after the 2000 season. 

6. John Riggins, Washington (1980)

Riggins wanted to renegotiate his $300,000 per-year contract entering the 1980 season. Washington refused. Riggins retired. The story could have ended there. 

But, thankfully for both the Redskins and Riggins, it didn't. One year later, in the summer of 1981, new Redskins coach Joe Gibbs decided to visit Riggins at his home to persuade him to rejoin the team. Gibbs, unbeknownst to Riggins, was hoping to trade the eccentric running back as soon as he agreed to come out of retirement. Gibbs got half of his wish. While Riggins agreed to come back, he would only do so if a no-trade clause was included in his contract. 

Riggins' no-trade clause would ultimately become a blessing for Gibbs, who rode the legs of his 33-year-old running back to a Super Bowl title in January of 1983. On his way to setting a then-NFL playoff record for rushing yards in a single postseason (610 in four games), Riggins earned MVP honors after rushing for 166 yards and the game-clinching score in Washington's 27-17 victory over Miami. 

Gibbs would win two more Super Bowls in D.C., while Riggins, eventually inducted into the Pro Football Hall of Fame, played five more seasons after sitting out the entire 1980 season. Both of their careers currently reside in the Pro Football Hall of Fame. 

5. Bo Jackson, Buccaneers (1986)

The 1985 Heisman Trophy winner, Jackson was deemed ineligible to finish his senior baseball season at Auburn after then Tampa Bay Buccaneers owner, Hugh Culverhouse, invited him to visit Tampa Bay's facility on his private plane. Jackson told ESPN in 2012 that he believed the Buccaneers, who assured him that he would not break any NCAA rules by attending the trip, intentionally set Jackson up so that he would not b able to play his senior year of baseball at Auburn (Jackson had not decided whether to pursue the NFL or MLB).

An angry Jackson told Culverhouse that he wouldn't play football if the Buccaneers selected him in the '86 draft. Tampa Bay did anyway, selecting the talented running back with the first overall pick. Jackson made good on his promise, sitting out the entire '85 season while making himself eligible for the '86 MLB draft, where he was drafted by the Kansas City Royals in the fourth round. 

After two productive seasons in Kansas City, Davis accepted then Raiders' owner Al Davis' offer to join Los Angeles after the Royals' 1987 season was over. Jackson enjoyed immediate success with the Raiders, averaging 6.8 yards per carry as a rookie. Jackson later became the first professional athlete to be named an All-Star in two major sports. 

4. Le'Veon Bell, Steelers (2018)

Bell had a monster 2016 season, amassing 1,884 all-purpose yards in 12 regular-season games before rushing for 167 and 170 yards in Pittsburgh's two playoff wins. But after not coming to terms on a longterm contract that offseason, Bell decided to skip training camp before signing his franchise tag before the start of the 2017 regular season. 

Everyone thought Bell would do the same after he again couldn't come to terms with Pittsburgh on a longterm deal heading into the 2018 season. They were wrong. 

Bell never returned to the Steelers, sitting out the entire season as Pittsburgh failed to make the playoffs for the first time since 2013. While the Steelers didn't rule out re-opening contract talks with Bell's representatives this offseason, Pittsburgh reportedly never spoke to Bell, who instead signed a four-year deal with the Jets that could end up totaling $61 million with incentives. 

While the Steelers did reportedly offer Bell a five-year deal that would have made him the highest-paid back in league history, the lack of guaranteed money in those contracts was ultimately what forced Bell to sit out and eventually leave town. 

Bell's legacy in Pittsburgh is complicated. While some fans are understanding of his prior situation, there may always be a percentage of Steelers fans who will never embrace Bell with open arms if he ever does decide to return to Pittsburgh for future team functions. 

3. Kelly Stouffer, Cardinals (1987)

Never heard of Stouffer? Don't feel bad. The former quarterback and Cardinals first-round pick in the 1987 NFL Draft never amounted to much in the league after sitting out his entire rookie season. A standout quarterback for Colorado State, Stouffer's contract talks with St. Louis got so bad that both sides ultimately gave up before the start of the '87 season. 

Stouffer later recalled a conversation during that time that took place between himself and then-Cardinals owner, Bill Bidwell.  According to Stouffer, Bidwell told him, "We don't have to do business like everybody else. You'll play for me or you will never play in this league." 

Bidwell eventually did allow Stouffer to play for another team, trading him to Seattle for several late-round draft picks just before the start of the 1988 draft (when the Cardinals' rights to him would have expired). Stouffer never materialized as an elite quarterback, going 5-11 as a starter and completing just over half of his career pass attempts in four years with the Seahawks. 

2. Eric Dickerson, Rams (1985)

Dickerson's 1985 holdout not only altered the course of his career, but it also caused extremely bitter feelings between himself and the Rams organization that would take over a decade to mend. 

After leading the NFL in rushing during his first two NFL seasons (including his history-making 1984 season that saw him rush for a league-record 2,105 yards), Dickerson sat out through the first two games of the 1985 season after not receiving a new contract. Dickerson eventually returned that season to help the Rams advance to the NFC title game. 

While Dickerson returned to lead the NFL in rushing in 1986, contract issues with the Rams continued to linger. The two sides finally divorced in 1987, when Dickerson was traded to the Colts during the season. While both sides continued to have success, the Rams of that era were never as good without Dickerson, and Dickerson was never as good as he was when he was with the Rams. 

The two sides finally mended fences in 1999, the year Dickerson was inducted into the Hall of Fame. The Rams awarded him a Super Bowl ring following their championship victory over the Titans in January of 2000. His No. 29 jersey has officially been retired by the franchise.

1. Duane Thomas, Cowboys (1971)

Bizarre is the best way to summarize the 1971 contract dispute between Duane Thomas and the Dallas Cowboys. After a sensational rookie season that saw him help the Cowboys advance to their first-ever Super Bowl, Thomas, who led the league in yards per carry average as a rookie, requested a revised contract entering the '71 season. 

Tex Schramm, the Cowboys' former general manager and a notoriously tough negotiator, didn't agree, resulting in Thomas sitting out Dallas' entire trading camp. The Cowboys then traded him to New England, where Thomas lasted just five days before the Patriots, in an unprecedented move, asked the league to reverse the deal after Thomas failed to get along with New England head coach John Mazur. The league did decide to reverse the deal, which sent a disgruntled Thomas back to Dallas. 

While Thomas begrudgingly played that season, he refused to talk to his teammates -- or coaches -- for the entire year.    

He may have been quiet around his team, but Thomas made plenty of noise on the football field. After leading the league with 11 rushing touchdowns in 14 regular-season games, Thomas was the star in Dallas' first Super Bowl victory, a 24-3 triumph over the Dolphins in Super Bowl VI. After the game, a game that saw Thomas dismantle Miami's "No Name" defense to the tune of 95 rushing yards and two touchdowns, he was asked by Hall of Fame running back and then NBC analyst Jim Brown if he envisioned having that kind of success against the Dolphins. 

"Evidently," Thomas replied. 

After flaming out of the league after just four years (he spent two mostly unproductive seasons in Washington after the '71 season), Thomas continues to be remembered by some of his teammates for his untapped potential that went largely unrealized. 

"I got the opportunity to play five or six years against Jim Brown," former Dallas Hall of Fame defensive lineman Bob Lilly told NFL Films in 2006, "and I just had visions of Jim Brown coming back to life because Duane, he had those same moves, the ones where you think you have him and he'd wiggle or he'd give you a limp leg. He could really go off tackle, about as good as I ever saw and start needing his way through the linebackers and secondary. Almost like music, in fact, I can see it right now."