Mets' Kodai Senga Could Have Future As Leverage Reliever

The New York Mets traded away just about every reliever that would be used in a high leverage situation by the Aug. 3 trade deadline, so somebody had to step up when closer Devin Williams was placed on the injured list with right shoulder strain.

In comes right-handed starter Kodai Senga, who was actually removed from the Mets' starting rotation due to massive, prolonged struggles through the first half of the season.

Senga, 33, carries a 7.79 ERA and 1.69 WHIP through 21 appearances (eight starts) this season, but as a reliever this month, he has a 2.45 ERA and has converted all four save opportunities despite being walked-off by the Chicago White Sox on Sunday.

This situation resembles that of Boston Red Sox pitcher Brayan Bello, who has also found success coming out of the bullpen in the later innings for Boston, according to MLB.com’s Mike Petriello.

MLB.com’s Jared Greenspan dove into why Senga is having success, modeling his findings off Petriello’s work, which was asking three questions: Did he change his pitch mix? Is he throwing harder? Is he being more aggressive in the zone?

Greenspan found that Senga, who has a six-pitch repertoire, is mainly throwing two of them – his four-seam fastball and forkball, nicknamed the “ghost fork.”

“Since the Trade Deadline, Senga is throwing his four-seam fastball (64%) and forkball (25.1%) a combined 89.1% of the time,” Greenspan wrote Tuesday.

“Why does this matter? Well, Senga's other pitches haven't been very good this year -- and that's putting it kindly. In at-bats ending against Senga's sweeper, slider, sinker and cutter, the opposition is hitting .364 with a .742 slugging percentage.”

With numbers like that, it’s no shock that he wasn’t succeeding as a starter. But as a high leverage reliever who is throwing just one inning per outing, Senga doesn’t need to throw the extra pitches.

Most starters who transition to the bullpen see an increase in their velocity, and that’s exactly what has happened with Senga. Greenspan discovered that when Senga throws under 97 mph, he gets hit way harder than when he’s surpassing that mark by a wide margin.

His control is still somewhat concerning, but he has been throwing the ball in the zone a little bit more than when he was a starter. According to Greenspan, his four-seam fastball zone rate is 1.7 percent higher compared to when he was a starter earlier this season.

All this to say that Senga could find extended success as a reliever late in games next season and based on how inconsistent Senga has been as a starter, the Mets may consider the full-time switch. Senga’s contract expires at the end of 2027.