MLB Daily DeltaWeek 25 · September 10, 2026
week 25
this weekBUY-LOW
last weekBUY-LOW

Geoff Hartlieb

ATH·P
data as of September 10, 2026·week 25
Buy Low fastball velocity stable and above league, the arm is fine; strikeout rate 14% is stable and well below league, limits the ceiling — luck-free xERA 3.97 sits 0.13 below league, a real arm the ERA is hiding; BABIP-against 0.328 elevated and unstable, bloating the ERA; buy the player, not the number.high 0.78
ROSK 3ERA 3.70WHIP 1.24W 0–0SV 0

Hartlieb is a buy-low — the bloated ERA is hiding a real arm.

His fastball is parked at 95.3 mph, a tick and a half above the league average of 94, and it has been climbing across the sample. That arm is not the problem — his ERA of 4.58 is. The number inflating it is his BABIP-against, .328 against a league average of .295, and that gap is luck, not skill. BABIP-against needs around 800 balls in play to be reliable; he has 65. Strip out the noise and his expected ERA is 3.97, .13 better than league. The contact he allows backs it up: 6.2% barrels against a league average of 8.0%. The catch is his strikeout rate, 13.6% and stepping down from his 19.6% career baseline — that caps the ceiling. The stuff is real; the surface is not. Buy low. Buy the dip for a 3 K / 3.70 ERA / 1.24 WHIP arm — deep-league only; the strikeout drain caps him as a spot streamer, not an asset.

VS His Norm

  • Strikeout %13.6%—−6.0% ▼vs his ~19.6% career norm

Drivers

  • xeraNOISEluck-free xERA 3.97 sits 0.13 below league — a real arm the ERA is hiding
  • babip_againstNOISEBABIP-against 0.328 elevated and unstable — bloating the ERA
  • p_fastball_veloSIGNALfastball velocity stable and above league — the arm is fine
  • p_k_pctSIGNALstrikeout rate 14% is stable and well below league — limits the ceiling
metric · nowrolling trajectoryvs. leaguestabilized?
Hard-Hit % Allowed41.5%
41.5%*
lg avg 40.0% ▲+1.5%vs his norm —
65 / 50 BBE
Barrel % Allowed6.2%
6.2%*
lg avg 8.0% ▼−1.8%vs his norm —
65 / 60 BBE
xwOBA Allowed.308
.308*
lg avg .315 ▼−.007vs his norm —xwOBA Allowed is below the ~.315 league average — expect it to rise.
88 / 200 TBF
xERA3.97
3.97*
lg avg 4.10 ▼−0.13vs his norm —xERA is below the ~4.10 league average — expect it to rise.
88 / 200 TBF
ERA4.58
4.58*
lg avg 4.10 ▲+0.48vs his norm —ERA is above the ~4.10 league average — expect it to fall.
19.7 / 200 IP
Strikeout %13.6%
norm13.6%*
lg avg 22.0% ▼−8.4%vs his norm −6.0% ▼
88 / 70 TBF
Walk %11.4%
norm11.4%*
lg avg 8.0% ▲+3.4%vs his norm −3.4% ▼Walk % is below his ~14.8% norm — expect it to rise.
88 / 170 TBF
BABIP Against.328
.328*
lg avg .295 ▲+.033vs his norm —BABIP Against is above the ~.295 league average — expect it to fall.
65 / 800 BIP
Swinging-Strike %11.7%
11.7%*
lg avg 11.0% ▲+0.7%vs his norm —
88 / 60 TBF
Chase %30.5%
30.5%*
lg avg 28.5% ▲+2.0%vs his norm —
88 / 60 TBF
Fastball Velo95.3 mph
95.3 mph*
lg avg 94.0 mph ▲+1.3 mphvs his norm —
308 / 50 PITCHES

5×5 ROS Outlook

rest of season

Where each category goes the rest of the way, and the skill that drives it. Tap a row to expand the full derivation.

statytdrosdriverconf
K% 13.6%→17.7%signal3 K — K% 13.6% (signal) lifted to career ~19.6% → projected 17.7% over ~7 remaining IP.
xERA 3.97noise3.70 ERA — xERA 3.97 (noise) blended 0% skill / 100% league 3.70 at 3 IP.
BB% 11.4% + contactnoise1.24 WHIP — a 11% walk rate plus BABIP-against 0.298 gives a 1.67 skill WHIP, blended 0…
run support + role0-0 W — wins ride run support and how deep he goes, not just skill.
role (middle)0 SV — role: middle, not in the save mix.
rosterdeep3.70 ERA, 1.24 WHIP

Every projection traces to a sabermetric input. The driver and confidence shown per row are always visible; tap any row to expand the full derivation.

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