It wasn't Michael Jordan, Kobe Bryant, or even LeBron James ... no, the toughest person Gary Payton said he ever had to guard was none other than John Stockton.
The NBA Hall of Famer made the shocking revelation in a chat about hoops with TMZ Sports ... saying the former Utah Jazz point guard was just that damn good.
"I think the hardest person I ever had to guard was John Stockton because of the way he would do 94 feet and go everywhere," he said. "That's my opinion."
'Stock', a 10-time All-Star who played 19 seasons in the NBA, was 6-foot-1, but 'The Glove' told us John's ability to utilize all the space on the court offensively made him a super difficult cover.
And, when Payton said he compared it to the trouble he had with MJ, LeBron and Kobe ... Stockton was just harder to deal with.
As for basketball's G.O.A.T. debate ... Payton weighed in on that too, telling us that while he believes LBJ is the better basketball player, Jordan was the better closer.
"I think LeBron was a better all-around player because he can pass the ball and rebound," Payton said. "I think Michael was a better killer. He'll go after you. He'll take a shot whenever he needed to and make it and do it. He was more of a killer."
But, check out the clip -- Payton's clearly still leaving some room for 'Bron to catch and pass Jordan in that category as well.