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Isaac Mattson

2026
Pirates· RHP · throws R· 36.2 IP· 4.91 ERA· 1.58 WHIP· 166 BF
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Grade

How good he's been, and at what
Fbetter than 25% of pitchers at limiting bases
RelieverStill Searching

Below league average across the board.

Mattson is getting hit harder than most pitchers

The simulator expects 0.471 bases allowed per batter faced against him — better than 25th percentile of qualified pitchers. His standout tool is HR Suppression (78th percentile). The soft spot is Quiet Contact (2nd percentile). Short relief stints inflate strikeout rates a touch, so read the Strikeouts spoke with that in mind.

166 batters faced · data through 2026-08-22.

How to read this chart
Each spoke is a skill estimate adjusted for sample size (not raw season stats), so farther out = better. Spokes are the metric itself; ↓ marks a rate where a LOWER number is better. Percentiles vs. 464 qualified pitchers — 100+ batters faced, starters and relievers pooled.

Plays like…

Same archetype, nearest by rate — pick one to see him side by side with Isaac Mattson.

Pitcher type

What kind of pitcher he is, next to the league

Pitcher type

Where he sits among qualified pitchers on the two skills that separate styles.

How to read this chart
Two skills separate pitching styles: finishing hitters without free passes (strikeout rate minus walk rate) and keeping the contact they do allow soft (hard-hit rate against). Every dot is a qualified pitcher this season; dot size tracks batters faced. Click any dot to open that pitcher's page.
 Isaac MattsonLeague medianPercentile
Bases per ball in play(lower = better).581.52825th
Walk rate(lower = better)11%9%26th
Strikeout rate(higher = better)21%22%39th

100th percentile = best in MLB.

Arsenal

What he throws, and what it does

Isaac Mattson leans on his four-seam fastball (72% of pitches). No pitch has beaten league-average results yet — the four-seam fastball has come closest.

Pitch mix & swing-and-miss

+2 bases better than a replacement arm this season

allowed 84 bases vs a replacement arm's 85 over the same batters faced

Replacement level is per-batter and can't be split by pitch type, so the bars below use league average.

All pitches

9.5 bases cost vs league average, across 689 pitches — 1.4 per 100.

Four-Seam Fastball
72%
94.1 mph · RHP median 95.1
20% whiffs · Lg median 21%
cost 0.6 per 1002.8 total
Slider
11%
84.2 mph · RHP median 86.9
27% whiffs · Lg median 33%
cost 3.5 per 1002.7 total
Changeup
10%
86.0 mph · RHP median 87.1
cost 2.6 per 1001.7 total
Sweeper
7%
83.0 mph · RHP median 83.5
cost 4.4 per 1002.3 total
How to read this chart
What they throw, how hard, and what misses bats — from pitch tracking, regular season only.

Mix by batter side

Four-Seam Fastball
72% vs LHH · RHP median 41%
71% vs RHH · RHP median 34%
How to read this chart
How the mix shifts against lefty and righty bats. Medians are among right-handed pitchers who throw that pitch at least 3% of the time — 351 of them. Overall results by batter side are under Platoon splits.

Isaac Mattson's pitch movement, 2026

His Slider and Changeup have moved 2+ inches from their early-season shapes.

Compared with his own earlier outings this season, not with other pitchers — and after taking out the drift every pitch in the league shows through midsummer.

Isaac Mattson's pitch movement, 2026-12-60612-6061218in← glove sidearm side →more risemore drop
Four-Seam FastballFF
Rise 17.9 in
+2.2 vs Lg median
Break 8.6 in
+1.0 vs Lg median
Vs. early season steady
SliderSL
Rise 3.6 in
+1.8 vs Lg median
Break −1.8 in
+1.9 vs Lg median
Vs. early season changed
ChangeupCH
Rise 3.5 in
−0.5 vs Lg median
Break 6.1 in
−8.0 vs Lg median
Vs. early season changed
SweeperST
Rise −1.0 in
−1.9 vs Lg median
Break −9.6 in
+4.3 vs Lg median
Vs. early season steady
Early season → nowLg medianCurrent-dot uncertainty
How to read this chart
Each dot is a pitch's current shape — horizontal break (arm side vs. glove side) by induced vertical break (rise vs. drop). Both axes are in inches of break. The trail runs from this season's earliest tracked outings — the faint, thin end — up to today's solid dot; a trail with only a few segments just means fewer tracked outings. The soft halo around each dot is how far that dot could sit off on its own, just from ordinary outing-to-outing wobble. Don't read a long trail as proof on its own that a pitch changed. Every pitch in baseball loses a little break through midsummer and gets it back by September — the same shift two full seasons back agree on — and the trail shows that league-wide seasonal swing alongside whatever this pitcher did himself. The sentence at the top of this card has the league's share taken out, so it can read “has not moved” above a trail that looks long. That is the two marks measuring different things, not a mistake. A pitch counts as changed only once it sits at least two inches from its own early-season shape — a verdict about this pitcher against himself, never a comparison with anyone else. League median: the small hollow ring marks it, on the same two measurements. Where it sits far from a pitch's dot, a line joins the two — and on a wider screen the ring carries that pitch's code as well — so a distant ring is never orphaned; where it sits close, neither is drawn, because the pairing is already obvious. League median is missing entirely for a pitch marked *: too few pitchers throw it for one to be worth setting, so it is plotted without a reference ring. For the exact dates a pitch changed, see the by-appearance chart below.

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)

Better vs RHB than vs LHB by 0.039 EB/PA allowed (modeled).

50% probable range: +0.031 to +0.048

vs LHB87 PA0.502

vs LHB: shrunk estimate 0.502 EB/PA, 50% probable range 0.480 to 0.523, based on 87 plate appearances. Raw (unshrunk) rate: 0.517 EB/PA. League median vs LHB: 0.454 EB/PA.

vs RHB79 PA0.463

vs RHB: shrunk estimate 0.463 EB/PA, 50% probable range 0.442 to 0.485, based on 79 plate appearances. Raw (unshrunk) rate: 0.502 EB/PA. League median vs RHB: 0.440 EB/PA.

0.4300.4550.4810.5070.533
← betterworse →
Below league medianAbove50% probable rangeHis raw rateMiddle half of the league

About the typical split for a righty arm (median 0.040). He allows more than the league median against both sides.

How to read this chart
  • Tap or hover any mark for its number, or tab to a row for all of them.
  • His raw rate is the unshrunk number against that side — small samples make it noisy, which is why the model pulls his estimate toward a more trustworthy value.
  • Middle half of the league” is the 25th–75th percentile of all pitchers against that side.
  • 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.
  • 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.

Contact allowed

What hitters do when they connect

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

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 Isaac Mattson landed this season.
How to read this chart
Dot color is estimated bases (EB) — what the contact was worth, regardless of what the defense did with it. So a dark hollow ring in the outfield is a crushed ball his defense ran down. Tap or hover a dot or a row to link the two, and use the ▶ links to watch a play on Baseball Savant.

Earned vs. actual

Results have matched the contact quality — batters have been credited about what they earned off Isaac Mattson.

Earned off his contact allowed66
Actually credited to batters62

over 113 balls in play · walks and strikeouts excluded on both sides

How to read this chart
Every ball in play is worth the bases its exit velocity and direction usually earn. Comparing those earned bases with the bases batters were actually credited shows whether his results have been lucky, unlucky, or fair.

ERA 4.91 · WHIP 1.58 · BABIP against 0.336 (Lg median 0.286)

Best games

His biggest outings this year

Best games

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

Multi-season trends · Isaac Mattson

HR allowed% down, BB% up, Barrel% against up, Hard-hit% against up, FB% against up, Pull% against up vs last season

Actual rates — what happened on the field, season by season.