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The San Diego Padres placed right-hander Yu Darvish on the injured list on Monday night with right elbow inflammation. In a corresponding move, the Padres promoted knuckleballer Matt Waldron from Triple-A El Paso. The team announced both moves on its official Twitter account.

Darvish, 37, admitted after his most recent appearance -- a four-inning, five-run start against the Milwaukee Brewers last Friday -- that he was dealing with fatigue. In 24 starts this season, he's compiled a 4.56 ERA (90 ERA+) and a 3.28 strikeout-to-walk ratio. Those marks are well below those he posted last season (122 ERA+, 5.32 SO/BB), when he finished eighth in National League Cy Young Award balloting.

Waldron, 26, made a pair of appearances for the Padres earlier this season. He surrendered seven runs on nine hits and four walks in 9 ⅔ innings. Back in March, Waldron talked to Sports Illustrated's Emma Baccellieri about his journey to the butterfly pitch:

At spring training in 2021, however, Waldron threw a few knuckleballs while joking around with some fellow pitchers. A team staffer took notice and made a request: Do that in front of the Rapsodo. The pitch-tracking device confirmed the desirably low spin rate, and so the team encouraged him to work on it, maybe even try it out in games. That year in High A, he began throwing it as a secondary pitch, just a few per game. Midway through the season, he got a message from the front office: What if he threw the knuckleball more often? Like, say, 80% of the time, starting the next week?

The Padres entered Monday with a disappointing 61-70 record on the season. San Diego is 20 games back in the NL West, as well as eight games back in the quest for the third and final wild card spot. In other words, the Padres are facing an uphill battle to make the postseason.