Zack Kelly

2026

Red Sox· RHP · throws R· 16.1 IP· 3.31 ERA· 1.29 WHIP· 71 BF

Grade

How good he's been, and at what

D36th percentile run prevention

RelieverPower Arm

Misses bats in bunches; lives with the walks.

Kelly has been below average at limiting damage

The simulator expects 0.471 bases allowed per batter faced against him — better than 36th percentile of qualified pitchers. His standout tool is Quiet Contact (73rd percentile). The soft spot is Command (20th percentile). Short relief stints inflate strikeout rates a touch, so read the Strikeouts spoke with that in mind.

Each spoke is a skill estimate adjusted for sample size (not raw season stats), so farther out = better.
Percentiles vs. 424 qualified pitchers — 100+ batters faced, starters and relievers pooled. He hasn't reached that bar himself, so he is measured against them rather than counted among them.
71 batters faced · data through 2026-07-29.

Plays like…

Same archetype, nearest by rate — the pitchers whose profile looks most like this one.

Yohan RamírezPirates

Luinder AvilaRoyals

Tyler SamaniegoRed Sox

Brock BurkeReds

Pitcher type

What kind of pitcher he is, next to the league

Arsenal

What he throws, and what it does

Zack Kelly mixes his cutter (44%) and sweeper (22%). His best pitch has been the sweeper, saving 1.5 bases per 100 thrown vs average.

Pitch mix & swing-and-miss

What they throw, how hard, and what misses bats — from pitch tracking, regular season only.

+4 bases better than a replacement arm this season

allowed 32 bases vs a replacement arm's 36 over the same batters faced

Results

All pitches

cost 0.8 per 1001.5 cost across 186

Cutter

44% +13 pts vs '25

90.6 mph · lg 90.1 −1.2 mph vs '25

19% whiffs · lg 20%

cost 1.9 per 1002.4 cost across 124

Sweeper

22% +1 pts vs '25

81.6 mph · lg 83.5 −0.3 mph vs '25

—

saved 1.5 per 1000.9 saved across 62

Sinker

17% +2 pts vs '25

95.9 mph · lg 94.8 −0.2 mph vs '25

—

Four-Seam Fastball

14% −6 pts vs '25

96.1 mph · lg 95.1

—

Changeup

4% −8 pts vs '25

83.6 mph · lg 87.2 +0.5 mph vs '25

—

Mix by batter side

How the mix shifts against lefty and righty bats. Overall results by batter side are under Platoon splits.

Cutter

44% vs LHH

44% vs RHH

By appearance

How the stuff has held up outing to outing

One point per outing — how his velocity, movement, and pitch mix have moved across the season, with league context for scale. Each pitch keeps the same color in every chart.

Platoon splits

How he fares against lefties and righties

Platoon splits (EB/PA allowed)

Dot = shrunk true-talent estimate; bar = 50% probable range. Tap or hover any mark for its number, or tab to a row for all of them.
Faint diamond = his raw, unshrunk rate against that side — small samples make it noisy, which is why the model pulls the dot toward a more trustworthy estimate.
These are bases allowed, so lower is better. Weighted by how often he faces each side, the two splits average back to his modeled overall EB/PA allowed — not the xEB/PA headline at the top of the page, which folds in strikeouts and walks differently.
Gray tick (marked “lg”) = league median vs that side; the faint gray band behind it spans the middle half of the league (25th–75th percentile).
Shrunk splits beat raw splits on held-out seasons, most decisively at low batters-faced counts (relievers especially), and converge with the raw numbers as exposure builds.

vs LHB21 PA0.458

Raw vs LHB rate (0.655) is off this scale — small samples like this are exactly why the shrunk estimate (the dot) is the trustworthy number, not the raw one.

vs RHB50 PA0.416

Raw vs RHB rate (0.374) is off this scale — small samples like this are exactly why the shrunk estimate (the dot) is the trustworthy number, not the raw one.

0.3810.4090.4360.4630.490

← better (fewer bases allowed)worse →

Better vs RHB than vs LHB by 0.042 EB/PA allowed (modeled).

50% probable range: +0.034 to +0.050

About the typical split for a righty arm (median 0.041). He allows more than the league median against both sides.

Contact allowed

What hitters do when they connect

Batters go to the pull side off him most often, but the hardest contact goes up the middle.

Pull and oppo are relative to each batter's stance, so this pools all the hitters he faced.

Batted balls allowed

Where every ball hit off Zack Kelly landed this season.
Dots are colored by estimated bases (EB) — pale slate (easy out) to dark teal (home-run territory).
Filled dots are hits; hollow rings are outs — a dark ring in the outfield is a crushed ball his defense ran down.
Tap or hover a dot or a row to link the two; use the ▶ links below to watch on Baseball Savant.

hit · out

EBlowhigh

vs Alec BurlesonHome run

EV 112 mph · LA 25° · EB 3.9

04/12 vs Cardinals

vs Kevin McGonigleOutRobbed

EV 100 mph · LA 21° · EB 2.0

05/06 vs Tigers

vs Gavin SheetsDouble

EV 109 mph · LA 16° · EB 1.9

04/05 vs Padres

vs Cam SmithSingle

EV 102 mph · LA 20° · EB 1.6

05/03 vs Astros

vs Jonathan ArandaSingle

EV 108 mph · LA 10° · EB 1.3

05/10 vs Rays

Luck check

Escaped damage once — a crushed ball the simulator scores as a near-certain hit died in a glove behind him.

vs Kevin McGonigleOutRobbed

EV 100 mph · LA 21° · EB 2.0

05/06 vs Tigers

Best games

His biggest outings this year

Best games

His best outings this season by bases saved vs a replacement arm.

Date	Opponent	Result	Bases allowed	Above replacement
May 1, 2026	Astros	6 BF · 2 K, 2 H	1.1	+2.0
Apr 22, 2026	Yankees	3 BF · 2 K	0.0	+1.5
Apr 20, 2026	Tigers	6 BF · 1 K, 1 H	1.6	+1.5
Apr 4, 2026	Padres	3 BF · 1 K	0.1	+1.4
May 12, 2026	Phillies	3 BF · 1 K	0.3	+1.2