Ex-NFL Star Thomas Jones -- Partiers Can't Be Winners ... In the NFL

If you wanna be successful in the NFL ... YA CAN'T GO PARTYING DURING THE SEASON ... so says ex-NFL running back Thomas Jones.

TJ -- who played 12 seasons and once led the AFC in rushing -- was out in L.A. last night when we asked if it's possible for NFL players to turn up on their off days ... and still ball out on Sunday.

"There's no NFL party time. The game is too hard for that. It's too physical and it's too strenuous," Jones says.

Of course, there are exceptions ... Joe Namath, Lawrence Taylor, Gronk ... but Jones says most athletes have to choose -- party or football.