How Kodai Senga became an ace in his rookie year

This story was excerpted from Anthony DiComo’s Mets Beat newsletter. To read the full newsletter, click here. And subscribe to get it regularly in your inbox.

When the Mets signed Kodai Senga to a five-year, $70 million contract last offseason, the move came with fewer guarantees than even the usual long-term deal for a starter. The history of pitchers from foreign leagues is mixed, ranging from the game’s top arms to some expensive disappointments. Despite all their scouting and all their research, the Mets couldn’t know for certain into which bucket Senga would fall.

The first hints arrived in Spring Training, when Senga dazzled teammates and opponents with his signature “ghost fork.” The regular season offered similar bursts of success, including an invitation to the All-Star Game in Seattle. But it was not until midsummer that Senga truly began morphing into the pitcher he would become. From the start of July through his final outing Wednesday, Senga went 6-2 with a 2.44 ERA.

“Outside of winning the Cy Young and just obliterating the league, it’s pretty close [to the best-case outcome],” pitching coach Jeremy Hefner said. “He didn’t really have to make any huge adjustments. He’s adjusted to the travel and to the ball and his teammates and the different stadiums and the different climates and all that kind of stuff extremely well. I couldn’t be more proud of him and how he’s gone about it.”

Senga’s most significant on-field adjustment was mostly abandoning his sweeper in June to focus instead on three pitches: a fastball he consistently ran into the upper 90s, a sharp cutter, and the ghost fork -- a pitch with unique action that profiles more like a splitter than a forkball. Entering Wednesday’s play, Senga’s ghost fork had the highest whiff rate of any single pitch in baseball, according to Statcast data. Another Statcast metric, Run Value, pegged Senga as the second-most effective pitcher in the National League behind Cy Young favorite Blake Snell.

What’s more, Senga’s walk rate dropped from 5.1 per nine innings over the first three months of the season to 3.3 per nine after that. He finished the year with 202 strikeouts, joining Dwight Gooden as the only Mets rookies to clear 200.

“When he got it going for two or three innings,” manager Buck Showalter said, “he could make it look easy.”

Asked about Senga throughout the season, Showalter consistently steered the conversation more toward the pitcher’s off-field challenges -- changes in culture, food, travel -- than his on-field ones. The Mets knew that they could ease Senga’s path between the lines, as they did in giving him extra rest for all but three of his starts. They couldn’t be sure how Senga the human being might react to pitching, for example, in frigid April conditions or steaming Atlanta summers. Neither could he.

“Honestly, going into the season, I had no expectations,” Senga said through an interpreter. “I had no idea what I was capable of.”

Now, everybody knows. The Mets have a baseline for Senga, a jumping-off point from which they can project his performance over the final four years of his contract. As he walked off the field for the final time on Wednesday, Senga did so as the Mets’ de facto ace.

The team believes he can maintain that sort of performance going forward, even if Senga’s focus has turned to other ambitions.

“Hopefully next year I’m no longer the ace because we get good free agents or good trades to power up our rotation,” he said. “It’s hard to throw for personal goals. Hopefully, the team is going to be a more winning team next year. Going into next year, I want to improve from this year. Whether I’m the ace or not, I just want to keep growing and getting better.”