After 34 pitches in Double-A, Michael Wacha enters the rotation of the St. Louis Cardinals

On April 26, 2010, Brandon McCarthy, who is currently pitching for the New York Yankees, was diagnosed with his third throwing shoulder "stress reaction" in four years while he was a member of the Oakland Athletics. According to his player card on Baseball Prospectus, McCarthy has since dealt with shoulder issues, ranging from soreness all the way to strains, on six different occasions since the start of 2011 (this will be revisited in the second half of this post*). On June 30, 2014, it was somewhat surprisingly reported that Michael Wacha, one of the Cardinals most prized pitchers, was diagnosed with a throwing shoulder "stress reaction" of his own. As General Manager John Mozeliak noted in this somber article from Derrick Goold, "At this point, he’s on the right track for pitching again this season. But we also want to be aware of what is needed to heal now and remain (healthy)."

Well, after nearly three months of rest and rehab, Wacha is set to rejoin the big league rotation, in a limited manner, after just one 34-pitch rehab start for the Double-A Springfield Cardinals. All things considered, Wacha's rehab start was promising, especially his fastball velocity (maxed out at 96 MPH per Tulsa radar gun). However, as was noted by Mr. Goold in the Best Podcast in Baseball, which was recorded prior to the rehab start, Wacha stated that "[his stuff] is not quite there yet. It's not where I need it to be—to be in a game." Mr. Miklasz quickly chimed in, "Well, does one start get all that back?" According to those that matter most within the organization, especially the Mercy medical staff, apparently one rehab start is enough for Wacha to rejoin the big league team and make the start against the Milwaukee Brewers tonight.

To be honest, this really isn't all that surprising given the arc of Wacha's rehab process. Before the specifics of the pitch count were officially reported through the media, I proposed the theory that Wacha's start would likely be limited to 50-60 pitches. Why? Because after a setback-free, 34-pitch outing, the next logical step is to ramp it up by a 20-25 pitch increment, usually in the form of another minor league start (complicated by Double-A Springfield's season being over, but conveniently resolved by Triple-A Memphis' involvement in the playoffs) or even a moderate-to-high intensity, extended bullpen session—one in which the rehabbing pitcher focuses on one or two things he deems necessary for success at the next level.

Well, as we all know by now, the next step in Wacha's recovery will consist of a workload limited to 50-60 pitches, but it won't be in the form of another minor league rehab start. Nope, it definitely can't be considered a moderate-to-high intensity bullpen session, either. Instead, it will be in the form of a major league start, in the midst of divisional race, against the Milwaukee Brewers—the same team the Cardinals had been chasing for months up until a few days ago. If the situation at hand is not an absolutely perfect example of the overused cliche of "night and day," then I really don't know what else could be.

Sure, the Brewers—losers of their last eight games—are slumping mightily and have been outscored 55-16 during this losing streak. As a team, they have a considerably less-than-stellar wRC+ of 92 in the second half (excluding last night's game since it's not yet updated as I write this). They will be without their All-Star center fielder Carlos Gomez (due to a sprained wrist) for the entire series, and the 2011 National League MVP Ryan Braun is in a big-time funk at the plate—slashing .233/.287/.415 since the All-Star break (again, excluding last night’s game). Of note, though, Braun has mashed changeups (Wacha's signature pitch) all season. All but one of these are positive signs for Wacha. However, at the end of the day, the Brewers are still a big league club chasing a playoff spot, and not a lineup full of minor league players (many being AAAA players, at best) in awe of the opportunity to face the 2013 NLCS MVP.

When facing big league hitters for the first time in roughly three months, I would assume a pitcher, especially one as young as Wacha, gets pretty "amped up." Though being "amped up" isn't necessarily a bad thing, it is still something to think about, especially with a pitcher who has much of his success via supreme command of two "straight" pitches—the fastball and the changeup. Will this negatively affect his performance in tonight's game? Will being "amped up" have a negative impact on the integrity of his mechanics and put him at an unfortunate risk of a flare-up, just two starts into his return? We will soon find out.

All that being said, I'm not all that worried about how Wacha is going to perform this evening. In fact, my worry level for tonight's outing, on a scale of one to Justin Masterson, is a two, possibly a three. Given Masterson's numbers as a starter since being acquired just before the deadline (7.90 ERA over 6 starts) and the fact that Wacha will undoubtedly be on a short leash, his performance shouldn't have too big of an impact on the game—unless, of course, he ventures to either one of the extremes (by no-hitting the Brew Crew vs. "many"-hitting the Brew Crew). Instead, my worry lies in the long-term health of the 23-year-old right-hander, and this is where I will briefly revisit the McCarthy-Wacha comparison.

*Michael Wacha is not Brandon McCarthy (thankfully). The way Wacha's body will respond to this injury could, and likely will, be vastly different to how McCarthy's did, and that can be attributed to the nature and beauty of human physiology. McCarthy has had flare-up after flare-up since 2007. For all we know, Wacha could have zero. Yes, three months of rest and rehab is a pretty long time for the body to recover. I am not about to deny this fact, but at the same time, this entire situation still seems slightly rushed. Those fully in favor of starting Wacha have pointed to four main things: 1) the slight cushion of a three game lead in the Central, 2) the availability of long-relievers Marco Gonzales and Tyler Lyons out of the bullpen, 3) what's the difference between 60 pitches in the big leagues versus 60 pitches in AAA (or elsewhere)?, and 4) finally, and probably most importantly, the fact that the medical staff has cleared Wacha to return to live action in the first place.

All four are very reasonable points, but the rarity of this injury in baseball brings Wacha's "medical clearance" into question, in my opinion. If the medical staff doesn't have past evidence/real-word examples to base their evaluations off of, then how can they be 100% sure? I have zero doubt in their expertise of reading MRIs and all the other diagnostic tests Wacha has been consistently receiving, but as with anything in the field of medicine, clinical endpoints (in this case, Wacha's future shoulder health) don't always follow what tests have shown or project to show (an evidence-based example is niacin and its lack of efficacy in reducing major vascular events despite lowering bad cholesterol and raising good cholesterol).

In conclusion, Wacha could follow the plan tonight, throw 60 or so big league pitches, and never experience a significant shoulder injury the rest of his career (best case scenario). On the other hand, the medical staff could have decided that it was best to slow down his rehab process or even shut him down completely, and still, he could have been plagued with shoulder injuries throughout his career. The future health of Wacha's shoulder is something that, unfortunately, Cardinals management, along with the team's fine medical staff, doesn't know for sure just yet. All things considered, though, especially given the unpredictably and volatility of the injury, I wish the Cardinals would have chosen to "err on the side of caution" with Wacha because I want to see the folowing for many years to come:

Have I mentioned that I absolutely love changeups?