Players · M · Pitcher · 2026

Isaac Mattson

Pittsburgh Pirates National League Central

Age: 31
B/T: R/R
Height: 6' 2"
Weight: 214 lb
Number: #72

Born: July 14, 1995 in Erie, PA, United States
MLB debut: May 7, 2021
Drafted: 2017, round 19
College: Pittsburgh

dbWAR: 1.0
IP: 38.2
ERA: 5.35
FIP: 3.72
K/9: 8.4
FIP−: 89

Isaac Mattson is a relief pitcher for the Pittsburgh Pirates. In 2026 he struck out 36 batters over 38.2 innings across 38 appearances, going 0-0. His ERA of 5.35 is 28.1% higher than the league average of 4.18 — 13th of 15 on his team, and 434th of 538 among MLB pitchers with 20+ innings. Stripping out defence, his 3.72 FIP suggests he pitched better than his ERA shows. He missed bats on 21.0% of swings (10.4% of every pitch he threw), walked 10.2% of the batters he faced and struck out 20.5%. His 0.5 dbWAR is built from that FIP rather than runs allowed, so it credits him for what he controls and not for the defence behind him.

League context

Percentile among qualified pitchers, 2026.

FIP3.72

K/98.4

WHIP1.60

WAR.5

WAR by season

Pitching

Standard and advanced, by season.


2026	PIT	38	38.2	0	0	44	23	36	18	5.35	3.72	1.60	8.4	4.2	128	89	0.5
2025	PIT	44	47.2	3	3	35	13	45	19	2.45	3.66	1.13	8.5	3.6	59	88	0.6
2024	PIT	3	5.1	0	0	1	3	6	5	5.06	4.29	1.13	10.1	8.4	124	105	0.0
2021	BAL	4	4.1	0	0	5	3	3	5	6.23	5.25	2.31	6.2	10.4	146	123	-0.0

Platoon splits

How left- and right-handed hitters fare against him.

Season

Opponent batting by the side the hitter bats from, 2026. Counted from play-by-play, so totals can differ from the box-score season line by a plate appearance or two.
Split	PA	AB	H	HR	BB	SO	AVG	OBP	SLG	wOBA	K%
vs LHB	92	80	25	2	11	17	.313	.391	.525	.397	18.5%
vs RHB	84	76	19	1	7	19	.250	.321	.342	.302	22.6%

Pitch sequencing

What Isaac Mattson throws in each count, and what he follows each pitch with. Select any cell for the breakdown.

ShowBatter

Four-seamSliderChangeupSweeper

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Pitch arsenal

What he throws, how hard, how often it misses, and what hitters do with it.

Season


Four-Seam Fastball	70.5%	513	94.2	2,352	51.7%	19.3%	108	.259	.737
Slider	12.1%	88	84.4	2,211	48.9%	27.1%	21	.429	1.190
Changeup	10.2%	74	86.0	1,250	29.7%	18.2%	10	—	—
Sweeper	7.3%	53	83.0	2,325	39.6%	28.6%	17	.235	.728

Isaac Mattson's arsenal by usage. Velocity is average release speed in mph, spin in rpm, and whiff rate is misses per swing — the cleanest single measure of whether a pitch beats hitters. BAA and OPS are what hitters did against each pitch, credited to the one that ended the plate appearance, and are left blank under 15 at-bats.

Head to head

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Similar players

Nearest 2026 seasons by command, run prevention and role, on rate statistics rather than totals.

José SuarezATH

ERA: 5.87
FIP: 3.85
SO: 61
WAR: 0.8

Very close

Connor SeaboldDET

ERA: 5.25
FIP: 4.27
SO: 20
WAR: 0.1

Very close

Cade GibsonMIA

ERA: 5.44
FIP: 4.05
SO: 43
WAR: 0.4

Very close

Juan MejiaCOL

ERA: 5.27
FIP: 4.17
SO: 66
WAR: 0.5

Very close

How these are computed

wOBA uses linear weights measured from this season's own play-by-play rather than published constants, and wRC+ is park-adjusted against that same league. dbWAR is our own open implementation — not fWAR or bWAR — and the full derivation, including its simplifications, is on the methodology page.