Cubs' key relievers might be regressing to mean at worst time

Some stalwarts in the Cubs’ bullpen might be regressing to the mean, and they sure picked a lousy time to do it. After starter David Peterson at least gave the Cubs a chance to win, pitching five innings of two-run ball, Trent Thornton all but removed it, allowing five runs in the sixth inning of an eventual 10-8 loss to the Reds at Wrigley Field. Thornton hadn’t allowed a run in August, spanning 10 innings in 11 games. But his ERA went from zero to 4.22 with the two-thirds-of-an-inning outing,…