The NFL legend heaped the praise on the Minnesota Vikings star this week ... calling him straight up, "the No. 1 wide receiver in the National Football League."

Of course, there aren't too many who'd disagree ... Jefferson, after all, has piled up a staggering 4,825 receiving yards and 25 receiving TDs in just 50 career games.

Then again, Chase, Hill, Kupp, Davante Adams and even guys CeeDee Lamb and A.J. Brown have been pretty good themselves.

Still, Moss made it clear Jefferson's his guy ... though he is at least somewhat concerned about what the loss of Dalvin Cook could do to the receiver's production this year.

"If there's anything that I have in question for the Minnesota Vikings and Justin Jefferson moving forward," Moss said, "It's what Dalvin Cook meant to that running game and the play-action passing game for Kirk Cousins and that offense."

"So," he continued, "I think that if they can move past Dalvin Cook still bringing that safety down in that box, it's still going to be just big numbers being put up by Jefferson."