Aaron Nola
- ERA
- 5.87
- SIERA
- 3.95
- FDI
- 141.75
The ERA looks broken. The fastball does not. Elite FDI and a SIERA almost two runs better say the run prevention is due to catch the heater, not the other way around.
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Deceptive Value Index
ERA–process gap · DVI 95.1 (#1 SP) ERA–process gap · DVI 13.6 Live model The full write-ups
The Fastball Deceptiveness Index (FDI) scores how much a four-seam fastball plays above its raw Stuff+. Hitters swing from patterns learned over thousands of looks: for a given arm slot and release height, the ball is supposed to arrive on a certain path. The deceptive heater bends that expectation, riding flatter or staying up longer than the familiar pattern predicts. FDI quantifies that deviation with HAVAA and AA, then multiplies it onto FanGraphs Stuff+.
FDI=FG Stuff+× ( 1 +0.15 · HAVAA+0.10 · AA)
Tap an input. The deception pieces (HAVAA, AA) are also the stickier ones. They carry more signal into next year than raw Stuff+ does.
2025 FDI vs. 2026 results. Stable year to year, and it forecasts swing-and-miss before the surface stats catch up.
0.868YoY stability
2025 → 2026 FDI
0.520→ 2026 K%
strikeout rate
0.506→ 2026 whiff%
fastball whiffs
−0.378→ 2026 xwOBA
lower is better
−0.435→ 2026 SIERA
lower is better
| Pitcher | FDI ↓ | Stuff+ | HAVAA | AA | ERA | SIERA |
|---|---|---|---|---|---|---|
| Jacob Misiorowski | 126.7 | 2.07 | 0.86 | 1.62 | 2.20 | |
| Didier Fuentes | 113.2 | 2.20 | 0.83 | 2.52 | 3.10 | |
| Joe Ryan | 107.9 | 2.12 | 0.42 | 2.85 | 3.19 | |
| Bryan Woo | 109.2 | 1.74 | 0.83 | 4.23 | 3.63 | |
| Payton Tolle | 113.9 | 1.23 | 0.97 | 3.14 | 3.93 | |
| Aaron Nola | 105.7 | 1.49 | 1.18 | 5.87 | 3.95 | |
| Kyle Harrison | 105.9 | 2.12 | 0.18 | 3.01 | 3.11 | |
| Bryce Miller | 110.4 | 1.11 | 1.01 | 2.18 | 2.86 |
Min. 200 four-seam fastballs. FDI, Stuff+, HAVAA and AA are the model's own 2026 outputs; ERA and SIERA are surface context.
FDI finds the nasty heater. DVI finds the starter whose ERA still hasn't priced it in. Starting pitchers only. High DVI = breakout case. Low DVI = regression case.
DVI=0.50 · FDI %ile+0.25 · FIP under ERA+0.25 · SIERA under ERA
| ERA–process board | FDI | DVI ↓ |
|---|---|---|
| Aaron Nola | 141.7 | |
| Chase Dollander | 136.1 | |
| Bryce Miller | 139.8 | |
| Bubba Chandler | 125.4 | |
| Jack Flaherty | 125.0 | |
| Justin Wrobleski | 115.2 | |
| Cole Ragans | 107.7 | |
| Connelly Early | 125.0 |
Top DVI among 2026 starting pitchers (min. qualification).
Zack Littell
- ERA
- 5.02
- SIERA
- 5.11
- FIP
- 6.21
- FDI
- 94.2 → 66.0
Deception collapsed year over year. ERA sits next to a matching SIERA and a worse FIP, so there is no quiet outperformance hiding under a soft surface line. Low DVI, falling FDI.
Qualified pitchers from the Shiny app: Pitcher Dashboard, League Explorer, Year over Year Correlation Lab, and Methodology. Slow to load? open in a new tab.