The Houston Astros’ starting rotation has made almost a miraculous turnaround this season. The starting pitchers’ performance has gone from extremely disappointing early in the season to among the league’s best over the last two months. What makes this improvement so surprising is that the rotation had to overcome an unprecedented number of injuries at the same time.
I have compared starting pitcher results before and after June 1, which constitute approximately equal samples of the season so far. Before June 1, the Astros’ rotation was ranked 26th in ERA. After June 1, the Astros’ rotation is ranked 3d in ERA, behind only the Mariners and Cubs.