The short version? The first year back from Tommy John is surely the most difficult, but if a player can return healthy, he stands a good chance of reclaiming his prior glory post-surgery...
The Hardball Times and the American Journal of Sports Medicine (AJSM) both did a studies of pitchers ager Tommy John surgery and their statistics post-surgery should they make it back to the major leagues. The Hardball Times found that a pitcher's ERA, BB% and K% are all between 4.5 percent and 6 percent worse than expected when compared to one year before the surgery. AJSM similarly found that ERAs are about 6 percent higher the first year back.
That said, a comparison to all pitchers in MLB that had the surgery doesn't provide an accurate picture of what we might expect from Harvey in his return. Harvey is a strong, young, ace-in-the-making, so he should only be compared to the pitchers that are similar to him: starters with a high baseline of performance, in the primes of their careers, who rehabbed properly and did not return early (recovery rates are much higher for young pitchers and for those who do not rush their recovery).
I decided to hand-select a more accurate cohort.
- Adam Wainwright, TJS performed in February 2011
- Stephen Strasburg, TJS performed in September 2010
- Tim Hudson, TJS performed in August 2008
- Chris Carpenter, TJS performed in July 2007
- K/9 down 2.11 percent
- BB/9 up 6.59 percent
- WHIP up 6.13 percent
- ERA up 3.19 percent
Even more encouraging is the huge step forward the group took in Year 2 post-surgery, actually posting numbers better in Year 2 than they did before undergoing Tommy John Surgery:
- K/9 down 9.64 percent
- BB/9 up 3.30 percent
- WHIP down 3.28 percent
- ERA down 4.46 percent
The first year back can be a little bumpy for the pitcher, especially with regard to a lack of command (walks in this group increased almost 7 percent in Year 1), but overall by the time Year 2 comes around the pitcher should be back to normal. Other recent examples not included in the cohort above tell the same story. Jordan Zimmermann and Josh Johnson both posted high BB/9 figures in Year 1 before lowering them in Year 2.
Putting aside the larger samples of data, the single best comparison for Harvey is Strasburg. Strasburg is, by far, the most similar to Harvey in stuff, in age and in his electric debut in the major leagues. Strasburg's recovery was a success, but he did take a notable step back from his meteoric major league debut, seeing an increase in his ERA of 24 percent (from 2.54 to 3.16) and an increase in his BB/9 of almost 40 percent (from 1.9 to 2.7).
Attempting to Project Harvey's 2015
Harvey's first two years in MLB were fantastic, as he posted a 2.39 ERA (2.33 FIP), 2.16 BB/9 and 9.88 K/9. I projected the the following adjustments for Year 1: -5% K/9, +20% BB/9, +20% WHIP, +25% ERA, along with Strasburg's innings cap, to give us the following projection for Harvey's 2015:
160 IP, 2.98 ERA, 9.4 K/9, 2.6 BB/9, 1.18 WHIP, 167 K
A 2.98 ERA might be considered a disappointment to some, considering Harvey's lifetime 2.39 ERA, but a 2.98 ERA would have placed him a very strong second on the Mets staff last season, trailing only Jacob deGrom (2.69) and miles ahead of Zack Wheeler (3.54). Furthermore, a 2.98 FIP would have ranked Harvey 15th in MLB last season (between Zack Greinke and Madison Bumgarner) so it is still a very optimistic projection for a player coming off major surgery.
Although there is a good chance that Harvey can outperform the above projection, there is also a decent chance that he might not return at all or will see significant setbacks in his recovery (the Hardball Times shows that about one in 10 TJS recipients fail to return to MLB.
As a fan, I'll take 160 innings and an ERA under 3 in a heartbeat, along with health and hope for the future.