2027 starter hook and bullpen roles
The question
How long should each starter go, and who gets the biggest bullpen spots?
Recommendation
Confidence MediumRotation (Winter Plan): Paul Skenes, Jared Jones, Braxton Ashcraft, Bubba Chandler and Mitch Keller. Two times through for Mitch Keller once his medicals clear. Let Braxton Ashcraft face the order a third time (a toss-up). Let Paul Skenes face it too, pending the review of his velocity drop. Jared Jones: a 22-batter leash (about 81 pitches) after his arm injury, not an open third time; past it, decide by matchup (a toss-up). Give Bubba Chandler development innings on a 22-batter leash (about 82 pitches), once through the top of the order a third time, at about 1.0 ± 1.2 runs against a two-times-through hook (a toss-up); the goal is first two passes at .306 xwOBA or better, not a third-time skill, pending the review of his velocity drop. Ladder: Mason Montgomery and Yohan Ramírez in the late innings (within noise of each other); Evan Sisk and Luke Weaver setting up (within noise of each other). Move Evan Sisk into the leverage ladder. Move Isaac Mattson out of it.
Decided together with “Mitch Keller: keep, trade, or add a starter” and “Extension: Paul Skenes”; all read the same Winter Plan.
The league step is stable every season and leverage is well measured. The per-pitcher calls rest on 2026 with 2024–25 at half weight, and a starter's own penalty barely repeats (r = 0.07). Mitch Keller's call holds only if he is healthy.
Evidence
- Hitters gain +.012 xwOBA the second time they face a starter and +.006 more the third, adjusted for pitcher and hitter quality (2024–26).
- The step is positive in each of 3 seasons; a starter's own third-time penalty barely repeats (r = 0.07), so the league step does the work.
- Pittsburgh starters reached a third time through in 80% of starts (20th of 30).
- Handing Mitch Keller's third-time batters to the 4th–8th relievers (.309 xwOBA after a second-look penalty) saves about 3.3 runs (≈0.3 wins) and adds about 29 relief innings, within a cap of 60. About 1.3 of those runs are the time-through-order step; the rest is the starter already pitching below those relievers.
- Leverage alignment 0.46 (18th of 30). Isaac Mattson got 9 high-leverage entries despite ranking near the bottom on skill.
- 40% of 2026's high-leverage entries left with Gregory Soto (34) and three relievers who left the organization during the season (24); the ladder in the recommendation ranks the plan's 2027 pen on skill.
- 2028: Luke Weaver's contract ends after 2027 ($12.5M), so his setup role reopens; next in the ladder is Wilber Dotel; Bubba Chandler is under club control through 2031 (Keystone's arbitration path), so his development innings pay off past 2027.
- Health in the rotation: Bubba Chandler: late-season velocity −1.3 mph and arm angle −3.2° against his baseline (last outing Sep 25); Mitch Keller: on the 60-day IL since Aug 3 (Right arm teres major muscle injury).
Options considered
| Option | Upside | Downside |
|---|---|---|
| Order-based hooks + skill-ranked ladderRecommended | ≈3 runs (≈0.3 wins); best arms in the biggest spots | ≈29 more relief innings to cover |
| Pitch-count hooks (status quo) | Familiar to players and staff | Ignores where the penalty happens |
| Openers and bulk relievers for back-end starters | Avoids the third pass | Needs a deeper, rested pen |
Risks
- Mitch Keller: on the 60-day IL since Aug 3 (Right arm teres major muscle injury); his call assumes he is ready.
- Bullpen capacity: the extra innings need a seventh or eighth reliever who can go multiple innings.
- Starters may resist shorter outings; framing it as a role, not a demotion, matters.
What would change our mind
If spring and early-season data show a starter's third-time results holding up, or the bridge relievers' quality drops.