Prior to being shipped to the Cardinals, Jake Westbrook's year looked suspiciously like 2007, when he went 6-9 with a 4.32 ERA. His xFIP this year is right in the same range. Considering that his lifetime xFIP of 4.02 was accrued in the American League, he must be thrilled to: (a) come to the National League; (b) come to St. Louis; and (c) come to Dave Duncan.
Westbrook's control is still coming back, but with the high ground-ball rate, he appears to be the perfect Dave Duncan candidate. I can see him putting up a 4.00 the rest of the way out and winning a few games on a good ball club. Assuming that he gets about 9-10 starts the rest of the way out, you could be looking at decent help here. While I would not break the bank on Westbrook (and if you are this late in the season and have a salary cap, it is difficult to do so), if you need a starter, you should go into the $40 range for Westbrook. You are not going to see much better the rest of the year.
P.S. In his first Cardinals start, Westbrook struck out 7, walked only 1, threw 61% strikes and induced 13 ground balls to 1 fly ball and 1 line drive. Dave Duncan, meet Jake Westbrook.