Star Athlete?
Chicago White Sox pitcher Bartolo Colón was benched after a shoulder injury in early 2009. In 2010 he didn't play in the major leagues at all. In 2011, his shoulder completely healed and his 95-MPH fastball restored, he was signed by the New York Yankees and became part of their starting roster -- thanks to a new medical technique many fans say is cheating.
In March 2010, Colón underwent a stem cell procedure in the Dominican Republic. The controversial treatment essentially regrew his rotator cuff using stem cells from muscle tissue. Critics of the procedure say it differs from "Tommy John surgery" (reconstruction of a ligament in the shoulder, first performed on a Los Angeles Dodgers pitcher in 1974, which appears to improve athletes’ strength) in that Tommy John surgery replaces damaged tissue while the therapy given to Colón builds new tissue. His supporters point out that this is no more than what the body does naturally, and the therapy merely facilitates it.
Major League Baseball has launched an investigation into the treatment, but has not so far found that it constitutes performance enhancement, which is prohibited by league rules.