An Opening Week Overreaction

Let's cut to the chase, Kodai Senga will win National League Rookie of the Year. As data-driven and meticulous as I like to be, it's always fun to ponder hot takes and overreactions. And so my overreaction after watching the first several days of MLB, is that Kodai Senga has already locked up Rookie of the Year. Senga opened the season at around +800 odds to win the award, right around Miguel Vargas and Ezequiel Tovar, with Corbin Carroll and Jordan Walker comfortably ahead. Senga's also only thrown 5.1 MLB innings. But again, Rookie of the Year may as well be his already.

Let's start with his success in NPB, which, if we've learned anything from the World Baseball Classic, as well as recent international signings (cough cough... Ohtani...), it's that NPB is a more than respectable and competitive baseball league. Senga pitched in Japan from 2012 to 2022, posting a 2.42 career ERA with a 10 K/9 and 3.4 BB/9. He also only allowed 0.6 HR/9. In his final season in Japan, 2022, Senga had a spectacular 1.89 ERA. Now with the Mets, Senga pitched 5.1 innings in his MLB debut against the Marlins, giving up 3 hits and 1 run on 8 strikeouts and 3 walks. Good enough for the win and quality start.

But Senga isn't your ordinary high strikeout pitcher. Representing 29.5% of his pitches on Sunday was Senga's signature ghost fork. Courtesy of Rob Friedman on Twitter, we have this overlay of Senga's 4 seam fastball (his most thrown pitch on Sunday) with his ghost fork, which looks like his fastball, but drops just as it gets to the plate, dipping just below bats and making guys like Jorge Soler here look like fools.

Seeing those pitches back to back is other-worldly difficult to put a bat on, let alone actually barrel up (speaking of, not a single ball was barreled by the Marlins against Senga). The forkball, along with playing extremely well off Senga's fastball, had a 64.3% whiff rate against the Marlins. The forkball is also an extremely rare pitch. It's similar to a splitter, but is slightly slower and has more vertical break. In the Statcast era, only two pitchers other than Senga have even thrown forkballs. Junichi Tazawa and Matt Carasiti are the two, neither of whom are starting pitchers, and neither of whom have pitched in MLB since 2019. The rarity of this unique pitch only adds to Senga's deception.

A little more deception occurs with Senga's tertiary pitch, the sweeper. Based on the spin on his sweeper, Statcast expects it to move with a 7:15 tilt, while it actually moves at an 8:15 tilt--60 degrees worth of spin-based vs actual movement deviation. Essentially, a fancy way to say it spins in a direction you wouldn't expect it to spin. It also has significantly more drop than the average similarly-moving pitch (4.7 inches more of drop to be exact). Senga's fourth pitch, his cutter, breaks 50% more than similar MLB cutters, and has 45 degrees of spin deviation.

With Senga, we have an experienced 30 year old with past results in a competitive league competing with guys in their low 20s making it to the big leagues for the first time. We have a guy who has deception on all four pitches he throws (including one pitch that most hitters likely have never seen). A guy who MLB hitters have minimal experience against. A guy who fanned 8 Marlins in his 5.1 inning debut. Obviously time will tell whether the hype behind Senga is a flash in the pan, but if he continues to deceive hitters like he did in his debut, it'll be really hard to convince people that anyone else is deserving of the NL Rookie of the Year Award.