The St. Louis Cardinals still lead the MLB with a 20-7 record and a 2.59 ERA, but the season-ending injury to starter Adam Wainwright has seemingly affected the performance of the starting rotation, which may put a strain on the bullpen.

It might not be much longer before general manager John Mozeliak considers a trade for the club to improve his cast of starters. The team was already involved in trade rumors regarding Cole Hamels, so it wouldn't be surprising. In the 11 games since Wainwright suffered his Achilles injury, the team's rotation has a 5.27 ERA and has seen nearly half of those starts last five innings or fewer.

The bullpen has picked up the slack and maintained a 0.97 ERA in 46 1/3 innings since Wainwright's injury, but reliever Jordan Walden suffered a shoulder strain this week and will miss six to 10 weeks. That will be a major loss because the right-hander had a 0.87 ERA and 1.065 WHIP in 10 1/3 innings this year.

If the rotation continues to struggle and the bullpen is affected by the starters' lack of deep outings, will Mozeliak take a look at the trade market?

"The 20-7 start has given GM John Mozeliak some time to assess the rotation without being influenced by the immediate pressure to make a panicky move to stop a losing rut," writes Bernie Miklasz of the St. Louis Post-Dispatch.

"...the Cardinals won't be able to go on like this all summer, putting a good bullpen at risk because of a rotation that can't deliver bulk innings. A 20-7 record looks fantastic now. But the Cardinals have 135 games left on the schedule, and trouble can find them."

ESPN Insider Buster Olney suggested starters Scott Kazmir of the Oakland Athletics and Mike Leake of the Cincinnati Reds could be made available in a trade before the deadline.

"Teams are combing over the early-season results and making assessments of their own needs, and on possible targets in the trade market that will develop in the weeks and months ahead," he wrote.

One of those teams is undoubtedly the Cardinals.

Kazmir, who the A's likely won't be able to afford after the season, and Leake, who will likely become a trade candidate if and when the Reds fall out of the playoff race, could be two veteran options for Mozeliak to consider. The two starters will become free agents after 2015, so the Cardinals wouldn't have to surrender an excessive amount in a potential trade, unlike a deal for Hamels, which would cost them at least two top prospects (as well as the remaining money on his contract).

However, Oakland may opt to keep Kazmir if they are in the postseason discussion in July because they'll still at least be able to get draft pick compensation for the left-hander when he likely turns down the club's qualifying offer after the season.

As for Cincinnati, the likelihood of them trading Leake will decrease if they're in the hunt, but the club might also be reluctant to trade him to the division-rival Cardinals even if they were willing to part ways with him.

Whether it's one of these two starters or somebody else, Mozeliak did not rule out making a trade before the deadline if the starting rotation was fails to produce through June and July. We'll see how the Cardinals do as the season progresses.