He may look like he's goofin' around, but Redfoo from LMFAO says he's deadly serious about a career as a PRO TENNIS PLAYER ... and he's been training his ass off to make it happen.
Here's the deal ... Redfoo has been a hardcore tennis fanatic for years -- and even dated former #1 women's player Victoria Azarenka for a few years.
And over the past few years, Redfoo says he's been studying the top players and putting in work -- and is 100% determined to be taken seriously as a pro player.
Check out the clip -- you can tell Redfoo means business.
The only problem is he's 39 -- old for an "up and coming" pro athlete ... especially since he failed to make the cut in a U.S. Open qualifier back in 2013.
But hey, anything's possible ... right?