Derek Jeter's haters can take a seat ... 'cause he ain't gonna let the Marlins suck forever -- so says legendary MLB boss Peter O'Malley.
O'Malley was the man back when he ran the Dodgers ... so we got him to give DJ a quick job eval -- after the Marlins CEO got DESTROYED in the media for trading away sluggers Giancarlo Stanton and Marcell Ozuna.
Peter told TMZ Sports Derek knows what the hell he's doing ... and we'll all see that eventually.
"Jeter’s gonna do a great job. He’s a very fine person, knowledgeable," O'Malley said.
Good luck!