Oswalt, 35, signed with Colorado back in early May. He made five Double-A tune-up starts, pitching to a 2.16 ERA and 0.93 WHIP in 33 1/3 innings. Last summer he went 4-3 with a 5.80 ERA in 59 innings for the Rangers after signing at midseason, a performance that earned him a demotion to the bullpen.
The Rockies have gotten a 4.41 ERA from their starters this year, which isn't all that bad considering they pitch half their games in Coors Field. Colorado is a half-game back of the Diamondbacks in the NL West at 37-34.