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Mets No. 1 starter Kodai Senga has been shut down for three weeks after receiving a PRP injection to counter his right shoulder strain, according to MLB.com's Anthony DiComo. Once the three weeks elapse, Senga will be allowed to begin a throwing program -- that means, clearly, that he will not be ready for Opening Day when it rolls around on March 28.

Earlier this month, Mets top executive David Stearns said Senga is dealing with a moderate posterior capsule strain. 

Senga, 31, was 12-7 with a 2.98 ERA (142 ERA+), 1.22 WHIP and 202 strikeouts in 166 1/3 innings last season, his first in MLB. He was likely going to be the Mets' Opening Day starter in 2024 until this injury. 

With Senga down, the Mets rotation will likely look toward José Quintana as the Opening Day starter, with Luis Severino, Sean Manaea, Adrian Houser and Tylor Megill behind him. 

There was an increase in Senga's workload last season from his last several years in Japan's Nippon Professional Baseball, though it wasn't a career high. He worked 180 1/3 innings in 2019. In the truncated 2020 season, he threw 131 innings. In 2021, it was 111 1/3 and then 148 in 2022. Then there was the jump to 166 1/3 last season, which shouldn't have been too much for his shoulder to handle. There are other adjustments in coming to MLB, of course, such as the travel schedule (there's only one time zone in Japan) and working on shorter rest. 

On the latter issue, there's a discussion point. Pitchers in NPB generally only go once a week, while the starter schedule in MLB is once every five days or so. The Mets did their best to softly adjust Senga. Four days of rest is considered normal in MLB, and he only took three starts on four days' rest all year. He started 17 times on five days and nine times on six or more days. 

Of course, this discussion could all be moot, as shoulder injuries happen to pitchers sometimes without a more specific reason than pitching is tough on the body.