The success rate for baseball players returning from shoulder surgery is awfully low, no matter what your definition of success is.
Some never make it back to the major leagues. Others do, but for abbreviated stints before they’re forced out of the game. Some, like John Danks, return, but aren’t as effective as they were before going under the knife.
Last year, FiveThirtyEight.com ran the numbers and found that only 67 percent of players who underwent a shoulder procedure returned to the major leagues (the rate for Tommy John surgery is 80 percent). For those pitchers who did return, they averaged 134 fewer innings per season than they did pre-surgery.