Statscape.(Baseball)

In a pennant race, managers sometimes ride their best pitchers harder. Days off allow them to skip that weak fifth starter, and extending a top hurler an inning or two can keep the more combustible relievers out of harm's way.

Overworking pitchers has costs, however, and not just the greater risk of injury. A longer-than-normal outing can produce a "hangover effect." In the annual publication Baseball Prospectus, authors Keith Woolner and Rany Jazayerli calculated that a 120-pitch outing raises a pitcher's ERA by 5 percent over the next three weeks--and even higher counts cause more painful hangovers.

That certainly has been true this season. Fourteen starters have thrown 130 or more pitches a combined 17 times; their next two outings have been worse compared with the rest of their season totals.

Of course, pitchers' endurance levels differ. Randy Johnson averaged 117 pitches per game while winning four consecutive Cy Young Awards. Supermen aside, though, most pitchers lose effectiveness after a grueling ...