Out of context, throwing a baseball for a living is not a particularly dangerous job. There are hundreds of other occupations that provide a greater threat to health on a daily basis than standing on a pitcher's mound. In the context of the game of baseball, however, pitching is a dangerous occupation. Besides the threat of a comebacker or awkward play at first base in which the pitcher has to cover, every pitch thrown during a game is a risk. Every pitcher in baseball is dealing with damage to his elbow in varying levels of severity, and as there's no telling how healthy a given pitcher's elbow is, the one pitch that could lead to serious injury is what makes the craft, in a word, totally unpredictable.
The success rate of Tommy John surgery is now so high that many fans take it for granted when an injury does occur, even going so far as to view it as some sort of rite of passage that every young pitcher must go through. But not everyone makes it back to the mound, and those that do are more likely to need another Tommy John at some point. We also know a lot more about how pitchers come back from Tommy John surgery than we used to, and it debunks a lot of previously-held beliefs.
On average, pitchers don't gain velocity, don't improve performance compared to their pre-injury numbers, and they're more likely to go on the disabled list with an injury to their throwing arm than a pitcher that didn't have surgery. While there is some evidence that TJ surgery might allow pitchers to not suffer as much age-related depreciation as those that have their original ligament, it's clear that this is a major surgery, and not something to be taken for granted.
With that said, there are a number of All-Star-caliber pitchers who are likely to make their return in 2016 (if all goes well), and they should be included in any analysis of the ongoing offseason transactions around baseball. 2015 was a particularly difficult year in terms of the talent of pitchers requiring Tommy John surgery, as a number of current and potential future aces had to undergo the procedure.
To help visualize the talent of the pitchers who had the procedure last year and could possibly return this coming season, I've plotted the average Wins Above Replacement in the year prior to pitchers undergoing surgery (I've set the lower cutoff at the year 2000, as it was the first year in which the number of surgeries was in the double digits). In other words, how collectively good were each year's Tommy John patients the year before they had surgery? Take a look:
In terms of performance in the year prior to surgery, 2015 was the third-"best" year in the past decade and a half, eclipsed only by 2008 and 2001. 2008 saw a collection of above-average pitchers undergo the procedure, as Tim Hudson, Sergio Mitre, Jake Westbrook, and Chris Capuano all had elbow injuries. 2001 claims the highest average WAR before surgery, as Pat Hentgen, Kris Benson, and Scott Williamson were some of the bigger names at the time to get TJ.
If we look at the raw total WAR of our pitchers instead of the average, 2015 is still third, but this time behind 2014 and 2012. This is because the number of surgeries has gone up markedly since the start of 2012; while the yearly average number of Tommy John procedures was around 17 from 2000-2011, it has spiked to an average of over 28 in the past four years.
Now that we concretely know the overall level of talent in our 2015 Tommy John class, let's take a look at the 2016 performance projections for a select group of starters that are expected to return in 2016. Dan Szymborski's ZiPs projections are used when possible, but if not available, Steamer was used instead (full ZiPs projections have yet to be released).
Yu Darvish, Texas Rangers
ZiPs Projections: 132.0 Innings Pitched, 3.41/3.45 ERA/FIP, 2.9 Wins Above Replacement
ZiPs projects Darvish to throw 132 innings in 2016, based on the assumption that he'll miss about a month of the season. The system also has him down for 2.9 WAR, second only to Cole Hamels among Rangers starters (3.7 WAR). The 2015 mid-season acquisition of Hamels, along with Darvish's likely return, put a good perspective on the Rangers depth moves of giving a minor league deal to A.J. Griffin and resigning Colby Lewis. While the back end of the rotation still has yet to sort itself out in light of these moves, the Rangers are primed to have two top-tier aces for the majority of the 2016 season.
Homer Bailey, Cincinnati Reds
ZiPs Projections: 149.0 IP, 3.93/3.85 ERA/FIP, 1.9 WAR
Bailey vaulted into the public eye with his 2012 and 2013 no-hitters, even though his year-to-year stats haven't quite matched the level of domination he showed during those two games. ZiPs is bullish on his ability to handle almost a full season of work in his return -- currently slated for mid-May -- and he will be an important, long-term part in the rotation of a team undergoing a serious rebuild. Attention should be paid to whether he can get his strikeout rate back to 2013 levels, as well as reversing the small erosion in control he suffered during the 2014 season.
Zack Wheeler, New York Mets
Steamer Projections: 65.0 IP, 3.69/3.63 ERA/FIP, 1.0 WAR
Wheeler's projections are difficult given the outstanding nature of the Mets' rotation. Currently, given a "June or July return," Wheeler would be battling for the fifth spot with Bartolo Colon, who New York just signed to a one-year deal. However, given that Wheeler is young, cost-controlled, and likely will still have the high-ceiling velocity of a potential ace, he makes (and has already made) an intriguing trade chip. While he could be a very useful swingman or fifth starter for the Mets during the second half of 2016, the embarrassment of riches they currently have at the starting pitcher position make a trade easily imaginable.
Alex Cobb, Tampa Bay Rays
Steamer Projections: 48.0 IP, 3.52/3.53 ERA/FIP, 0.8 WAR
While the Steamer projections are on the low side given the expectation of a midseason return, Cobb is one of the most interesting names on this list. In addition to his name recently cropping up in trade talks with the Cubs, Cobb posted two seasons of at least 140 innings pitched and sub-3.00 ERAs before he was injured, flashing completely un-hittable stuff at times. His changeup ranked as one of the five best among starters by run values during 2014, and if he can avoid the pitfalls of decreased control (something he has had difficulty with already) following surgery, he could pick up right where he left off.
Brandon McCarthy, Los Angeles Dodgers
Steamer Projections: 48.0 IP, 3.20/3.20 ERA/FIP, 0.8 WAR
Given the way this offseason has unfolded so far for the Dodgers, it's not a stretch to say they would welcome a healthy McCarthy back into their threadbare rotation. Coming off his first 200-inning campaign in 2014, it looked like McCarthy might have put his injury history behind him while posting some of the best numbers of his career; his elbow unfortunately had other plans. Still, the right-hander always seems one adjustment away from putting it together. Despite his strong ground ball rates, he's been victimized by home runs over the past few years, and even outstanding gains in his strikeout rate couldn't mask the problem. The Dodgers will be hoping for a repeat of 2014 when McCarthy returns sometime in June or July, because it seems like they might truly need it after missing out on some of the top names in the free agent pitching market.
Finally, there are a couple intriguing relievers who could see a return to the field in 2016 after undergoing surgery last season. The most exciting is Adam Ottavino, who has three different sliders and looked dominant in his short stint as the Rockies' closer during 2015. Greg Holland, who had surgery just this past October, will likely not see the field until 2017 unless his recovery is miraculously short.
While it might be easy to forget about pitchers who have stepped out of the spotlight due to injuries, 2016 hopes to be a banner year for the return of ultra-talented pitchers from serious surgery. With any luck, these starters and relievers will be added to the long list of success stories, primed to pitch again.