Crew coach Robert Warzycha revealed to the Columbus Dispatch that the 23-year old was joining in pre-season training to see if he had what it takes to play at the top level.
McAfee is still contracted to the Colts but is just believed to be testing himself in a different environment which Warzycha explained, adding that you never know what may come up in the future.
"He wanted to be in a pro environment and try it out," said Warzycha.
"I don't think we would close the door to anybody just because they play a different sport.
"We'll see what happens next. I don't think we'll take him to Phoenix (for preseason camp), but he can play and he knows the game. He kicked the (heck) out of a few balls."