2025 stats: 8 G (7 GS), 29.2 IP, 6.37 ERA / 4.00 xERA, 11.8 K/9, 5.2 BB/9, 1.55 WHIP, +0.3 fWAR
It’s down to Kai-Wei Teng and Tristan Beck as the players left in the organization following the flurry of
trades former President of Baseball Operations Farhan Zaidi made at the 2019 trade deadline. Both were pitched as starters, but it turns out that both might wind up as relievers.
In Teng’s case, that is a very positive development, as despite his terrible performance as a starter, he showed aptitude in shorter bursts — or in the bulk innings role following an opener. But since the Giants are organizationally resistant to that strategy over the course of a season, let’s zero in on Teng’s likely role going forward.
The trendy-because-it’s-really-effective pitch these days is the sweeper. Kai-Wei Teng threw his 38.7% of the time duromg his MLB service in 2025. Batters hit .191 off of it with an expected slugging percentage of just .256. In a very limited sample size, it was about as effective as Shohei Ohtani’s sweeper, Chris Bassitt’s, Trevor Roger’s, Mitch Keller’s, and Dylan Cease’s. Remarkably, based on the quality of contact, it had the same expected batting average (.167) as Paul Skenes’s. But that’s hardly the point!
The point is that relief pitchers are usually 1 or 2 pitch pitchers. As a starter, his fastball velocity sat more in the 92-93 range, but as a reliever he’s more in the 94-95 range. That’s really effective paired with that sweeper. 21 of his strikeouts came off that best pitch while 10 more off that fastball, meaning 31 of his 39 strikeouts (79.5%) came on just those two pitches… which really does cement his best role being that of a relief pitcher.
It was an unusual route he took to getting to this position, though. For many, he was an afterthought, and the Buster Posey-led organization’s behavior only supported that. They designated him for assignment after the 2024 season, an action that was among the first taken by the Posey administration. Just 10 days later, they signed him to a minor league contract to bring him back into the organization.
Why make that move? They almost certainly had his stuff pegged and had the opportunity to bring him back into the organization presumably because they knew he’d clear waivers. Because they didn’t outright him, they still maintain that flexibility down the road if they need to shove him off the 40-man roster for whatever reason. But more immediately, he still has 2 major league options remaining; so, there’s plenty of time to sort out a proper role for him.
It’s worth noting that on the day of his callup (August 1st), Eno Sarris posted this analysis regarding Teng’s Triple-A measurements:
Giants SP Kai-Wei Teng has interesting arsenal. Wide, no standout pitch.
[Four seam] / 241 thrown / 90 AAA Stuff+
[Sinker] / 107 / 95 Stuff+
[Sweeper] / 324 / 106 Stuff+
[Cutter] / 107 / 102 Stuff+
[Changeup] / 49 / 102 Stuff+
[Slider] / 30 / 101 Stuff +Only Sweeper has above-ave locations —> fits his command grades.
The Giants rolled the dice to clear a roster spot but knew they had something to work with if they could retain him. I’d hope that the number-based discussion to this point would prove sufficient evidence for those who are skeptical, but at the end of the day, the analytics, the results, and the Giants actions demonstrate that the organization is glad to have him on the 40-man roster heading into Spring Training.
Teng pitched his way into being the next in a line of perfectly serviceable back of the bullpen arms. Maybe close to already improving upon Spencer Bivens and Tristan Beck — just from a stuff standpoint — and, at worst, even with Carson Seymour in the upside reliever role — if they had to establish the depth chart today. His strikeout totals are impressive. In September, he K’d 27 in 16.1 IP and had this tidy little highlight against the Dodgers:
He struckout out Shohei Ohtani with his four-seamer in the 1st inning and then with the sweeper in the 3rd. He got Mookie Betts, Andy Pages, and Freddie Freeman with that sweeper, too. Michael Conforto struck out on Teng’s changeup.
Teng is a wild arm that’s still a work in progress. He’s still best known for getting shelled and putting too many runners on base. In that strikeout-laden September (28 K%), he still walked too many (12.2 BB%) and hit too many batters with stray pitches (4 — with 7 on the season). But, he allowed just 1 home run in the final month and just 2 across his innings.
His results are far from great but they were clearly good enough to thrust him into a meaningful conversation the organization has held all offseason. He’s definitely “pitching depth” that should be confidently mentioned in a conversation about that very subject — not quite on the level of the outlandish statement made by last season’s pitching coach, J.P. Martinez, but certainly as a factor in the team covering innings in 2026. While I don’t personally believe he pitched his way into a backup starting pitcher role, he’s certainly an option if they need to do some bullpen games or as an injury or blowout replacement to give the team multiple innings.
He’s a big guy (6’4”, 241 lbs), so, I like the durability potential here, and I suspect the Giants do, too. Most starters wind up sustaining their careers as relievers, and it looks like that’s the course Kai-Wei Teng managed to chart for himself in 2025.
