Pittsburgh Pirates at Chicago Cubs: Final Score & Recap

The Pittsburgh Pirates handed the Chicago Cubs a 4-3 defeat at Wrigley Field on September 13, 2026, overcoming a deficit that the DiamondIQ model's estimate made look unlikely — Chicago had entered the night with a 59% win probability and never reached 0% slower than in that final out. The Cubs drew first blood in the bottom of the first on a run against Pittsburgh starter Bubba Chandler, and Miguel Amaya extended that lead with a two-run home run in the fifth inning, a swing that shifted win probability 25.2 percentage points in Chicago's favor and briefly made the Pirates' path to victory look narrow. Pittsburgh answered emphatically in the top of the sixth, stringing together the decisive damage against Aaron Civale and Matthew Boyd. Brandon Lowe's single moved the needle 18.9 points toward Pittsburgh, and Nick Gonzales followed with a double off Boyd worth another 17.0 points, part of a three-run frame that put the Pirates ahead 4-3 and fundamentally reordered the game.

From that point, Pittsburgh's bullpen protected the lead with efficiency. Luke Weaver was the most impactful arm on the night, contributing 23.3 percentage points of win probability, including a pivotal eighth inning in which Nico Hoerner's groundout cost Chicago 12.9 points of win equity. Carmen Mlodzinski added 19.1 points of his own, and Caleb Thielbar closed out the Cubs' remaining chances. The most decisive moment of the game came in the bottom of the ninth, when Carson Kelly grounded out against Mason Montgomery to end the contest, a play that registered plus-31.6 in WPA simply by virtue of extinguishing Chicago's last realistic path to a comeback. Amaya finished as Chicago's top performer by WPA at plus-23.7, while Gonzales was Pittsburgh's most productive bat on a rate basis, posting a 0.7 RE24 alongside his 15.0 WPA contribution.