St. Louis Cardinals right-hander Jake Westbrook was shut down just a few pitches into his bullpen session Saturday.
Cardinals manager Mike Matheny said it was ''not a good day'' for Westbrook, who will be re-evaluated Sunday.
Westbrook suffered a strained right oblique Sept. 8 and postponed his bullpen session Friday. He is 13-11 with a 3.97 ERA in 28 starts this season.
The Cardinals, who play the Chicago Cubs on Saturday, will start Lance Lynn Monday in Houston in Westbrook's slot. Jaime Garcia will pitch Tuesday, and Chris Carpenter starts Wednesday.
Carpenter made his season debut Friday and allowed two runs in five innings.
St. Louis holds the second wild card spot by 1 1-2 games over the streaking Milwaukee Brewers.