Reggie Bush is such a huge fan of USC quarterback Caleb Williams ... he tells TMZ Sports he thinks there's absolutely no ceiling on what the signal-caller can do with a football in his hands.
"He's a great young kid," Bush told us out at Dash Radio in Los Angeles this week. "The sky is the limit for him."
Of course, Bush would know a thing or two about the topic ... he balled out at SC from 2003 to 2005 -- and then went on to have a solid 11-year NFL career.
Clearly, he believes Williams can do the same -- and even more -- telling us he's stoked to see what the 21-year-old can do following his Heisman Trophy campaign last season.
Bush says he's actually spoken to Williams in person before ... and called their meet-ups "amazing."
As for when Williams -- who transferred from Oklahoma to USC prior to last season -- eventually gets to the pros ... Bush said there isn't one team in the league that should pass on him in the 2024 NFL Draft.
"Anybody can use him!"
Trojans season kicks off in August -- ya can bet Bush will be locked in!!