Pittsburgh Pirates at Boston Red Sox: Final Score & Recap

The Pittsburgh Pirates handed the Boston Red Sox a 4-1 defeat at Fenway Park on April 5, 2023, overcoming a pre-game DiamondIQ model estimate that placed Boston's win probability at 54%. Pittsburgh built its lead methodically across the middle innings, finishing with nine hits and no errors while Boston committed two errors in a five-hit performance that never generated consistent offensive pressure.

The game's single most consequential play came in the top of the fourth, when Carlos Santana connected on a home run off Corey Kluber, a swing the DiamondIQ model valued at a 11.3-percentage-point shift in Pittsburgh's favor. Santana added another impactful moment in the top of the seventh with a double off Kaleb Ort worth 7.7 percentage points, finishing as the game's top offensive performer at plus-12.0 WPA and plus-1.6 RE24. Bryan Reynolds contributed a key double off John Schreiber in the top of the sixth, adding 7.1 percentage points of win probability, while Andrew McCutchen finished at plus-4.8 WPA and plus-0.9 RE24. Boston's best chances evaporated on the bases and in the box: a Rafael Devers double play in the bottom of the sixth off Mitch Keller cost the Red Sox 8.0 percentage points, and Masataka Yoshida grounded into a double play in the ninth off Duane Underwood Jr. to close the door at minus-7.7 percentage points.

Mitch Keller was the dominant force of the evening by the DiamondIQ model's accounting, finishing at plus-31.3 WPA to lead all pitchers by a wide margin. Kluber added plus-7.5 WPA in a losing effort on the Boston side, and Rob Zastryzny contributed plus-5.2 WPA in relief for Pittsburgh as the bullpen protected a lead that Santana's bat had established and the Pittsburgh defense, without an error on the night, helped preserve.