Hayden Birdsong Raised His Slot. Will Warren: Curveball Extraordinaire

Hayden Birdsong, Will Warren, Nick Martinez

• Giants Hayden Birdsong goes 5 IP, 5 H, 6 K in his return to the rotation. He’s made some changes compared to last season. His arm angle has kicked up from 42° to 48°, now higher than ~81% of MLB pitchers. This has caused him to cut his four-seamer more, losing 3” arm-side, but gaining 2” vertical break. It now averages ~19” from his well-above-average 6.6’ release. FanGraphs Stuff+ improved his four-seam grade from an 80 to a 99. On top of the arm-angle change, he’s shifted 10” toward the third-base side of the rubber. The higher slot has also caused his slider shape to gain velocity and thus vertical break. It averaged 86 mph with 1” vertical break and 1.5” glove-side last year. It’s up to ~88.5 mph this year with 5” vertical break and 2” glove-side. He’s also using the slider more to righties, pushing it from 27% to 38% while he’s backed off his curveball. His slider has also made its way into his lefty gameplan at the expense of four-seam. 🤔

  • Birdsong’s stuff is good, the concern is more about his locations and ability to throw strikes. He ran just a 61% strike rate out of the bullpen (would love to see 65%), and he was in zone just 46%, something just 2 qualified SPs are doing this season (Freddy Peralta and Carlos Rodon). He ticked up to 53% in this start, but it was mainly due to his slider feel rather than fastball. Slider-first could be an approach that works, given his feel of the pitcher at this higher interval of velocity, it’s just unorthodox. Command is what to watch here, I’m not convinced he has the zone rate to be a <4.00 ERA starter until I get more sample.

Hayden Birdsong’s Kick-Changeup grip (2025)

• Yankees Will Warren with a 2.38 ERA / 1.67 FIP over his last 4 outings after a career-high 10 strikeouts last night. In April, he threw his new curveball just 13% of the time to left-handed hitters in two-strike situations. Over these last 4 starts, he’s up to 33% usage, and the pitch is running a 56% whiff rate with 52% chase. FanGraphs Stuff+ has the curveball as his highest-graded pitch, sitting 80 mph with -11” vertical break and 14” sweep. His four-seam usage is also up against lefties from 39% to 50%, with the main increase coming in the first or second pitch of an at-bat against a lefty (43% to 62%). 🗽

  • Nothing dramatically different against righties of late, but a fun nugget is that he hasn’t allowed a fly ball on his sinker in May. Warren is sitting on a 4.05 ERA this season, clearly on the upswing. Even if I’m a bit worried that the HR rate will shoot back up against lefties, unless this curveball is really this good, it’s still a sub-4 ERA pitcher for me rest of the season, which is more aggressive than any other public projection system.

Will Warren’s curveball (May 20, 2025)

• Reds Nick Martinez’s 4.40 FIP in his first 5 starts is down to a 2.36 in his last 5. His cutter to lefties ran a 23% barrel rate in his first 5 starts with a .498 xwOBAcon. He’s cut his usage of the pitch in half to 13% and is mixing in more four-seamers. The cutters he is throwing to lefties have been pushed inside more. His righty zone rate has jumped from 48% in those first 5 starts to 57% in his most recent 5, a dramatic improvement. He’s also allowed just one righty barrel in his last 57 balls in play (1.8% barrel rate). The 34-year-old remains a location and command god. I’ll take the under on a 4.20 ERA projection rest of the way. 👍