The couple secretly saw each other in Florida while A-Rod was at spring training, according to U.S. tabloid magazine Life & Style.
"A-Rod's with Cameron. They've been keeping it quiet, but they're totally together," a source told the weekly.
Witnesses at the Creative Artists Agency Super Bowl party described them as flirting and dancing before leaving together at the end of the night. But a source told the Post that their relationship is casual, with neither pushing for commitment.
Despite that, he was linked to a series of Miami beauties including Elaine Spottswood and gorgeous Wilhelmina model Melissa B.
Reps for A-Rod and Diaz could not be reached for comment.