What Happened to Paul Skenes?

After back-to-back sub-2.00 ERA seasons and the 2025 NL Cy Young, Paul Skenes is sitting on a 3.83 ERA through 29 starts. This dashboard digs into the pitch-level Statcast data for an explanation. The short version: the strikeout stuff is intact and his FIP says he's pitched closer to a 3.16, but he has already blown past last season's full-year home run total, and the fastball has lost a tick.

The ERA says collapse. The FIP says otherwise.

Cumulative ERA and FIP by start. Opening Day (5 ER in ⅔ of an inning against the Mets) left the ERA at 67.50 after one start, so the chart begins at start two. From mid-April to mid-June he ran an ERA between 2.36 and 3.00. Since then the rough nights have kept coming: seven runs in Philadelphia on July 1, five apiece against the Cubs and Reds in late July, five more against the Giants on September 1. He has steadied a bit lately, with two scoreless outings in his last five, but the ERA line has flattened out well above the FIP line instead of falling back toward it. Red dots mark home runs allowed: they cluster in exactly the starts where the ERA line jumps.

The home runs have a fingerprint

The arsenal, 2025 vs 2026

Whiff rate is down on nearly every pitch. The changeup and slider still miss bats, though hitters are doing far more damage on the changeup when they do connect. The sinker's whiff rate has fallen from 15% to 11% and the splitter is getting hit at a .339 clip. The curveball, a real weapon in 2024, is basically shelved at under 1% usage.

Usage and velocity deltas vs 2025. Green = improved, red = worse. Whiff% = swinging strikes per swing. BAA hidden under 10 at-bats.

The quiet warning sign: velocity

Average four-seam velocity by start. He opened the year at 97.9, has sat under 97 in most starts since mid-May, and the 95.7 against Miami on August 11 was his lowest of the season, two and a half ticks under his 2025 average of 98.2. It has held between 96.6 and 97.2 in the four starts since, so this looks like a step down that stuck rather than a slide that is still going. Nothing here screams injury, but it is the one thing on this page that isn't explained by luck.

So what actually happened?

Three things, in order of importance. First, home runs: he has allowed 15 in 155.0 innings after allowing 11 in 187.2 all of last year, and they're concentrated on fastballs over the middle. Second, the blowups: Opening Day and July 1 alone account for 12 of his 66 earned runs, and taking those two out drops his ERA to 3.23. That was a cleaner story in June than it is now, though. Eight of his 29 starts have cost him four or more earned runs, so this is no longer a case of two bad nights dragging down an otherwise clean season. Third, the stuff is a half-grade duller: the fastball is down 1.3 mph and whiff rates are down across the arsenal. Not enough to make him bad, but enough to shrink the margin for error that made 2025 look easy. The strikeouts are still elite at 10.5 per nine, the walks have crept up from 2.0 to 2.6 per nine, and FIP still has him as a top-of-rotation arm. This reads less like a decline than like a great pitcher having a merely good season, with the home runs doing most of the damage.