Senga, who will turn 30 on Jan. 30, has been in Nippon Professional Baseball since 2010. He was originally drafted as a developmental player by the Fukuoka SoftBank Hawks as a 17-year-old.
The Hawks added him to their official roster in April 2012, and the right-hander has been one of the best pitchers in NPB for the past 11 seasons. He has been named to the All-Star team three times and led the Pacific League in strikeouts in back-to-back years in 2019 and 2020.
Senga didn't post an ERA above 3.51 in any of his 11 NPB seasons. He announced in October, following the Pacific League Climax Series, that he was going to exercise his opt-out rights to test the waters in MLB.
MLB.com's Anthony Castrovince ranked him as the No. 5 pitcher and No. 11 overall free agent this winter. Even though he will almost certainly sign as a starter, there are questions about his long-term ability to last in that role in MLB.
Per The Athletic's Keith Law, Senga's fastball gets up to 100 mph "with a plus splitter, while opinions on his slider vary from below-average to just slightly above."
Law did note Senga also throws a curveball that could "be at least an average pitch," but his below-average command and general questions about feel for pitching lead to some doubt about his ability to turn over a lineup multiple times.
It would be a surprise if New York doesn't at least let Senga try to start. It wouldn't be difficult to shift him to the bullpen later this season or even later in his career if things don't work out as expected.
The Mets have completely revamped their rotation from last year. Jacob deGrom left for the Texas Rangers in free agency, and Taijuan Walker departed for the Philadelphia Phillies. Chris Bassitt remains on the market.
However, New York has replaced the trio with American League Cy Young winner Justin Verlander, left-hander Jose Quintana (2.93 ERA last season) and Senga. Max Scherzer and Carlos Carrasco remain from last season to round out the rotation.
There's no doubt that pitching depth was something the Mets needed to target this offseason, especially with the free-agent losses.
Plus, Carrasco and Scherzer are both over the age of 35. The Mets are going to need pitchers who can soak up innings during the regular season.
Senga has overpowering stuff that should play nicely in whatever role he ends up in.