The Red Sox lost the opener of a two-game home series against the Reds, 2–1. Down by two runs in the bottom of the ninth, Boston had runners at second the third with no outs, but were only able to score once. Starter Michael Wacha allowed one run on three hits in innings and took the loss. The Red Sox ended May with a record of 23–27, in fourth place in the American League East, games behind the division-leading Yankees.
