Michael Wacha is the biggest wild card for the Cardinals rotation in 2015

Michael Wacha spent most of the 2013 postseason as a hero as he pitched well and the Cardinals won four of the five games Wacha started in the playoffs. It would be terribly unfair to label Wacha as the goat of the 2015 postseason, he was at least a lamb as Mike Matheny put him on the mound in the ninth innings of a tied Game Five of the NLCS with 19 days rest. In between, Wacha got off to a blazing start to the 2014 season before an unusual injury derailed his season. With proven performers like Adam Wainwright, Lance Lynn, and John Lackey, and the tantalizing abilities of Carlos Martinez, the Cardinals rotation should be good. Michael Wacha has the ability to make the rotation great.

Take these two players through June 1st of last season:

The lines are not identical, but they are close. Player A is Michael Wacha and Player B is Adam Wainwright. For two months last season, Wacha continued his postseason success into the regular season. He pitched at an ace level. Wacha made three more starts in June as his struggles began, and his attempt at coming back in September was met by less than stellar results. Here are the same two players from June 1st to the end of the season:

While there might be something of a cloud hanging over the end of Wainwright's season, he pitched incredibly well through injury without his best stuff. Wacha, in just his first full major league season, was shut down due to his unusual shoulder injury. Due to that shutdown and struggles in his attempt to come back, Wacha has some questions entering Spring Training. Jay Jaffe of Sports Illustrated wrote that Wacha's health was "The Big Question" for the Cardinals heading into camp.

[T]he Cardinals are going to have to watch their prized 23-year-old righty closely, and since he's never thrown more than 149 2/3 innings in any of his three professional seasons - and just 109 last year - they can't count on him for a full 200-inning workload. Even so, he probably has the highest upside of any pitcher on the staff save for ace Adam Wainwright, so the situation certainly bears monitoring.

Signs are encouraging thus far. In Derrick Goold's story about Wacha's arrival to camp, the Cardinals' pitcher sounded upbeat about his progress.

"The ball is coming out right, and I'm happy with that," Wacha said. "I want to continue to get stronger during spring training, getting all of those pitches back, getting the command down. I felt good. I feel strong when I'm on the mound. The arm has been bouncing back, well, something that I'm really happy with at this point. Everything has been going well."

There have been a lot of questions about Michael Wacha's mechanics and offseason regimen. When he returned late last season, he was throwing fewer changeups, raising questions whether the injury had affected his pitch arsenal. In order for Wacha to return to the dominant pitcher he showed in the 2013 playoffs and the first few months of last season, he needs to have his full complement of pitches.

Wacha throws four pitches: fastball, cutter, change, and curve. All four of those pitches were used at least ten percent of the time in the first two months last season and all four pitches achieved successful results. From Brooks Baseball:

Looking just at whiff rate, we can see how important Wacha's fastball-change combination is to his success (League averages from this post at FanGraphs):

Wacha's cutter and curveball are decent pitches, but as we saw last September, he cannot survive unless he has his changeup working. All four in concert make his fastball that much better. Last September, Wacha's whiff rate on his fastball was down to 9.36%. That number is still above average, but nothing compared to the one generating nearly twice as many swings and misses as the league average. Given the volume of fastballs Wacha throws, getting those swings and misses can make a big difference to his overall numbers.

The good news for Wacha is that he has not had to adjust his mechanics, according to this story from Jennifer Langosch at MLB.

While the Cardinals have spent several months learning more about the injury -- it is officially termed a shoulder stress reaction -- that shut Wacha down in June, there has been no call for the right-hander to adjust his mechanics to prevent future issues. Instead, the only tweaks made to Wacha's schedule have come in his off-the-field work, where he's added some new exercises designed to build strength around his right shoulder.

"It's a pretty rare injury, and a lot of people don't know how it happened or how to fix it rehab wise," Wacha said. "I'm continuing to get stronger, and hopefully I'm building the muscles around the injury to where it doesn't happen again."

There will continue to be some trepidation with Wacha's starts going forward. While Wacha is getting ramped up for the season, his mechanics and pitch selection will be a major focus in determining his status. We will not have a lot of information until Wacha gets himself in game shape. There is no clear solution to fixing and preventing Wacha's injury, but strengthening his muscles around the shoulder makes a lot of sense. Brandon McCarthy has pitched with the same condition that Wacha has, strengthened his shoulder and performed well in over 200 innings pitched last season.

The Cardinals will likely spend a lot of time worrying about the number of innings they are receiving from their starters. For Wacha, what he does with those innings is far more important. Wainwright, Lynn, Lackey is a solid 1-2-3 for a rotation, but a potent Wacha could make that rotation great or at least keep it at a high level if another player should suffer an injury. Wacha is a wild card this spring. He has shown the ability and results to pitch at the top of any rotation. Getting back to that level could be pivotal to the Cardinals' season.