August 10, 2011

Painting the Black

What to Expect from Strasburg

by R.J. Anderson

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Two wonders of the baseball world were on display on Sunday afternoon in Hagerstown, Maryland, when the city—home to the Nationals’ Low-A affiliate, the Suns—received the honor of hosting Stephen Strasburg’s first rehab start. One of the wonders was Strasburg himself, what with his perfect pitching frame, lurid fastball, Bugs Bunny slider, and capable changeup. That combination formed the basis for his impressive 12 major-league starts last season, helping him meet the unreal expectations born from surreal hype and establish himself as the best young pitcher in baseball. One didn’t have to look away from Strasburg’s arm to spot the other wonder: a four-inch long scar on his right elbow, an artifact from his Tommy John surgery.

The comedian Louis C.K. has a bit where he highlights the relentless expectations of human beings. Everything is great, he says, but nobody is happy. C.K. is talking about technology and the absurdity of complaining about how long a cellular signal takes to reachspace, but he could have been talking about Strasburg or Tommy John surgery. In September of 2010, Strasburg’s ulnar collateral ligament had frayed or torn to the point that he could not throw a baseball without pain. Eleven months later, Strasburg returned to the mound and hit 98 miles per hour on the radar gun, but the wondrous nature of his return was lost on some observers who took the medical near-miracle for granted.  

Saving a pitcher’s livelihood through surgery is no longer a notable achievement, despite Tommy John surgery being a relatively new procedure. Medical technology has advanced to the point where you almost hope that an injured pitcher is dealing with a popped UCL rather than a torn labrum or rotator cuff—yes, he might miss most of the next year, but at least you can expect him to return.  As it is, the failure rate is almost never considered, since there is an assumption that the pitcher will put in the hours to strengthen and rehab his elbow. Prospectus alum Thomas Gorman wrote about the ins and outs of Tommy John surgery back in 2004. BP later republished Gorman’s work with some added quotes courtesy of Will Carroll in June 2009, and it remains a must-read. Below is an excerpt that adds perspective:

Pitching overhand is a particularly stressful motion; the strain it puts on a player's joint is commonly injurious. Sometimes the UCL will weaken and stretch (technically a sprain), making it incompetent. Other times a catastrophic stress will cause the structure to "pop" or blow out. The injury isn't tremendously painful, and it can be incredibly difficult to diagnose without sophisticated imaging (such as an MRI), but incompetent or blown out, a damaged UCL will prevent a player from throwing at full velocity or with effective control.

Until recently, a UCL injury was career-ending or, at the very least, a major detour in a career path. Some believe that Sandy Koufax's "dead arm" in 1966 was simply a case of a damaged UCL. It is unknown how many pitchers prior to 1974 could have benefited from this type of procedure, but given the rate of surgeries today and what we know about the workloads of the past, it is reasonable to assume that one out of every ten or so pitchers who burned out or simply faded away might have been saved.

While Gorman’s final point is still true, Corey Dawkins’ creation of an injury database has illuminated an otherwise unexplored area of baseball analysis. For instance, did you know that since the dawn of the 2001 season, 122 major-league pitchers have undergone Tommy John surgery? That works out to about 12 pitchers per season, without including pitchers who had the procedure while in the minor leagues.  Of the 116 pitchers who went under the knife before 2011, 18 have failed to return to the majors.

Ostensibly, Strasburg will not join that fraternity—heck, he may appear in the majors before this season is over, if only to kiss a few babies and shake a few hands—leading the conversation in the direction of what to expect moving forward. This topic has become popular at The Book blog, where Tom Tango has gone as far as to post polls on the subject and compare Strasburg to Francisco Liriano. Even the most logical people in the room were expecting a full return, which is a testament to how skilled the folks who perform the procedures and oversee the rehabs are—that outcome seems rarely in doubt.

Still, one has to ask whether undergoing Tommy John surgery generally means worsened post-surgical performance. Thanks to the Adrian Gonzalez of querying, Dan Turkenkopf, the table below could take shape. The first column specifies how many innings were required at the major-league level before and after the surgery to be included in the sample. From there, there are measures of observed improvement or decline, Earned Run Average and Fair Run Average—an increase or decrease of 0.10 runs is the threshold, which works for the purposes of this observation.

More than half of the pitchers saw their ERAs and FRAs worsen, but don’t fret too much, since there is an inherent survivors bias at work here. Bad pitchers do not last long in the major leagues, and while it would be foolish to dismiss all the cases of failure, you have to consider the sample size here, too. What the 54 cases of worse ERA tell us is that the pitchers who reached the major leagues before and after ligament replacement surgery allowed earned runs at a higher rate following the surgery, for whatever reason.

The reason isn’t always strictly health-related. Take Jorge Campillo. He completed two innings in the majors and avoided allowing an earned run before having Tommy John surgery. After the procedure, he threw 180 2/3 innings in the majors and allowed 4.23 earned runs per nine innings pitched. On a net basis, his ERA jumps by 4.23 runs, but it’s hardly likely that the pre-injury Campillo was going to sustain a non-existent ERA.

Ultimately, the sample size limits the analytical options for this data, but the cumulative numbers for every pitcher involved are listed below. Note that while the overall ERA increases, the FRA dips. Neither shifts by a significant amount, mind you, but overall, it does not appear that Tommy John surgery has had too drastic an effect on pitchers besides keeping them around.

Although it may sound outlandish, there is recent precedent for a young stud of a pitcher to undergo Tommy John surgery and return with a better ERA than before. Had Josh Johnson qualified, he would have finished with the second-best ERA in the National League in 2006. He then spent the next two seasons injured and recovering before returning. Johnson had a 3.10 ERA in that 2006 season, but he has a 2.80 ERA since returning from the surgery in 2008. Strasburg probably won’t reach that level, but just having him healthy and active again will make the game more entertaining—and we owe Dr. Frank Jobe our gratitude for that.

R.J. Anderson is an author of Baseball Prospectus. Follow @r_j_anderson
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