Mustain was one of the nation's top high school quarterbacks and played his freshman year at Arkansas in 2006 before transferring to USC. After going 8-0 as a freshman for the Razorbacks, he became stuck behind Mark Sanchez, and then Matt Barkley, on USC's depth chart.
Mustain, 23, hasn't pitched since high school and was prepared to report to the Georgia Force of the Arena Football League, but in a tryout with the White Sox, his fastball cracked 90 mph on the radar gun.
"I haven't played in eight years, which, my age, it's going to be a little bit harder to get back into this," Mustain said, according to 5News in Fayetteville, Ark. "As time goes I figured this would be my one shot at it, and why not? I'm going to take this shot. I'm going to give it everything I have and see where it goes."
Mustain told 5News that the White Sox believe they can work toward raising his velocity into the mid-90s with proper instruction. He said he will keep open the possibility of returning to football if his baseball career doesn't pan out.
"I'm confident that I'll get back in shape quickly for it," Mustain said, according to 5News. "They're going to give me the opportunity to face batters and get my feet wet no matter what happens to me. If I'm getting tagged right off the bat, I'll just keep plugging away."
Despite a disappointing football career at USC and an arrest last year for trying to sell medication he was taking to treat his attention deficit hyperactivity disorder, Mustain remains confident he will succeed in sports.
"I'm going to play one sport or the other until somebody tells me to go home," he said, according to 5News, "until they're not even going to let me try. So I'm going to go do it and literally throw everything I have at it and see where it goes."