I'm sure there's a stat on this somewhere... but it'd be interesting to see how many athletes from other sports have tried boxing, and how many have had some kind of success. The more well-known are ex-football players, as in the NFL or college football. One of the early ones was "Too Tall" Jones, a huge lineman for the Dallas Cowboys who tried and failed miserably at boxing. Some other lineman from the New York Jets tried it also, and I believe met with the same results.

On the flip side, it seems Hershel Walker is trying to hang on in MMA.