Mr. Wonderful ain't exactly shy when it comes to his opinion ... and the "Shark Tank" star just let Magic Johnson know why the NBA legend done MESSED UP by quitting the Lakers.
Kevin O'Leary wasn't disrespectful -- in fact, he likes Magic a lot -- but he thinks the guy made a huge mistake Tuesday night by suddenly stepping down as Pres. of Basketball Operations.
"He made a decision which I think was the wrong one," Kev told us on his way out of ABC Studios in NYC.
"The Lakers are in chaos. The opportunity is to stay onboard during chaos and fix it ... and I think he should have done that."
O'Leary -- who's also close with Mavs owner Mark Cuban -- believes LeBron James played a role in Magic's decision to leave.
"I'm speculating like everybody else is ... but [Magic] probably had a disagreement between a very influential player and other management."
Ultimately, Kevin thinks the breakup is as nasty as they come -- comparing the split to a marriage falling apart.
Sad, considering O'Leary thinks Magic has all the right talents to right the ship in L.A.