Listen up, pro tennis players ... Rich Paul is offering some free business advice -- explaining to TMZ Sports he believes a career switch to pickleball could yield huge benefits for athletes if they officially traded in rackets for paddles.
Paul broke it all down for us at LAX this week ... about a month after he, Patrick Mahomes, Naomi Osaka, Nick Kyrgios and others joined forces to own a Major League Pickleball team.
The founder of Klutch Sports Group said he believes the sport is awesome and about to take off -- and noted that if a pro tennis player made the switch over now, it might lead to a big windfall of cash and fame later on.