The rotation currently ranks fourth in the majors with an ERA of 3.23, and they've received production from every starter.
After missing all of 2011 recovering from Tommy John surgery, it's taken Wainwright some time to get back to full strength.
Jaime Garcia, the other guy expected to anchor the rotation in Carpenter's absence, has actually been the team's second-least reliable starter—albeit with a 3.55 ERA.
Garcia owns a 3-2 record, but opponents are hitting .300 against him. His WHIP is a gaudy 1.41.
Although the team's top two active starters haven't been as successful as the Cardinals expected them to be thus far, there's no way that Carpenter's return will effect their status as members of the rotation.
One of the final three starters—Kyle Lohse, Jake Westbrook or Lance Lynn—will be given the boot once he's ready. But, the question is, who will it be?
Lohse has been great this season, posting a 5-1 record with a 2.91 ERA.
His ERA will likely increase as the season progresses, but there's reason to believe that he can keep up his success. Last season, Lohse went 14-8 with an ERA of 3.39.
Westbrook has also exceeded expectations, recording a 2.41 ERA and a 4-3 record.
It's highly unlikely that he'll continue his success though, as he hasn't posted an ERA lower than 4.00 since 2004 with Cleveland (3.38).
Lynn has been the biggest surprise for the Cardinals. Nobody expected him to lessen the impact of the loss of Carpenter, but it can be argued that he has performed better than Carpenter would have.
Lynn is tied for the major league lead with seven wins and has posted a 2.54 ERA in the process. Opponents are hitting just .213 against him.
Out of the three starters in question, I would have to say that Westbrook will be given the boot, assuming that Lynn can keep up his success.
There would definitely be teams interested in acquiring the services of Westbrook, so he could become a valuable trade chip.
Carpenter isn't likely to return until the end of July, so manager Mike Matheny will have plenty of time to make a smart decision.