The Tokyo Yakult Swallows have reportedly reached an agreement with right-hander Koyo Aoyagi, according to multiple reports. Although the team has yet to officially announce the move, it would mark Aoyagi’s return to Nippon Professional Baseball after just half a season stateside. Until now, he had spent his entire NPB career with the Hanshin Tigers.
Koyo Aoyagi will likely test out the MLB market via the posting system this offseason.
Even at his best, Aoyagi was a command-first sinker-baller, but has fallen on rough times the past two seasons.
Any success stateside will ride on his highly deceptive low sidearm slot. pic.twitter.com/yt9u28kyo1
— Yakyu Cosmopolitan (@yakyucosmo) November 4, 2024
Aoyagi, 31, joined the Philadelphia Phillies on a minor league deal via the posting system on Jan. 17, 2025. Despite a solid spring training, he spent the season shuttling between Double-A Reading and Triple-A Lehigh Valley, where he struggled to a 7.22 ERA and 2.05 WHIP across 33 2/3 innings. He was subsequently released on July 23.
2 Ks in a clean inning of relief for Koyo Aoyagi 👏pic.twitter.com/HId2rhcajh
— Yakyu Cosmopolitan (@yakyucosmo) March 5, 2025
Aoyagi was a model of consistency from 2016 to 2022, posting a sub-3.40 ERA and maintaining a ground-ball rate near 60 percent in each of those seven seasons. His peak came between 2021 and 2022, when he turned in a sparkling 2.26 ERA across 49 starts. He led the league in wins in both seasons and, in 2022, captured the Central League ERA title and earned CL Best Nine honors.
However, the Yokohama native saw a sudden drop-off in 2023, as his ERA+ plummeted from 156 over 162 1/3 innings in 2022 to just 69 across 100 1/3 frames the following year. 2024 wasn’t much better, as he posted a 78 ERA+ and a career-worst 113 FIP over just 12 starts, falling out of favor with Hanshin manager Akinobu Okada. One of his few highlights during that stretch came in Game 7 of the 2023 Japan Series, when he delivered 4 2/3 scoreless innings to help the Tigers secure their first championship since 1985.
青柳のヤクルト移籍について
阪神には枠が無かった、仕方がない。藤浪みたいにもう少しメジャーで頑張って欲しかったが、メジャーの再オファーも全く無さそうだった。となると藤浪の様にNPB移籍からのメジャー復帰を目指す形を取るのが妥当。pic.twitter.com/tK8RbXQkXf
— うらびー (@urabi00) July 25, 2025
Much of Aoyagi’s career success can be attributed to his unorthodox style—a sidewinding, nearly submarine delivery—and his ability to command the zone as a sinkerballer. He’ll need to rediscover some of that form to be an asset for Yakult, who enter the All-Star break with NPB’s worst record at 28-50-5.
Aoyagi also won’t get much help from their defense, which ranks last in the Central League with minus-40 Defensive Runs Saved. What he needs now is an opportunity to prove himself again, and he’ll be afforded that in a low-pressure environment with the Swallows.
Some have raised concerns that the posting system is becoming a loophole for players to reach free agency more quickly. Aoyagi signed with the Phillies despite slim odds of reaching the MLB and now returns to NPB with a fresh start. Similar criticism has been directed at players like Naoyuki Uwasawa and Kohei Arihara.
On the other hand, some argue that this trend serves as a counterbalance to NPB’s strict domestic free agency structure, ultimately benefiting all parties involved. It gives players more mobility while allowing teams to recoup their posting fees. And, of course, players don’t pursue opportunities in the U.S. intending to fail.
WBN Japan: https://worldbaseball.com/league/japan/
Photo: WikiCommons
