Bob Costas explains first pitch blooper to Jimmy Fallon, insults 50 Cent on The Tonight Show

Bob Costas is on a crusade. 

Mr. St. Louis himself has been on a one-man tour of the country trying to rationalize his second take of a first pitch at Busch Stadium last season.

Back in November, Costas made an appearance on MLBN's Hot Stove with Bill Ripken (subbing for Harold Reynolds) and Matt Vasgersian to plead his case. Costas explained that the first pitch was actually being filmed as part of a PSA to air in St. Louis and they needed a shot of then-Cardinal A.J. Pierzynski catching the ball. So when Costas realized he botched the take, he asked for a mulligan.

Yeah, we weren't buying it, either. But on Thursday Costas appealed that decision and took his case to a higher court ... The Tonight Show with Jimmy Fallon. Once again, Costas laid out the facts and attempted to convince viewers that it was professionalism -- not vanity -- that fueled the second take.

Oh, and he managed to insult rapper 50 Cent in the process: