The ex-Cincinnati wideout made the claim to TMZ Sports just ahead of the Bengals' season-opener ... saying the team's star quarterback is simply that good at the moment.

"He's top five," T.J. said of the 25-year-old signal-caller. "I don't know who comes out of the top five, but in no particular order, when you ask me who are the top five quarterbacks, I'm going to say Patrick Mahomes, Aaron Rodgers, Joe Burrow, Justin Herbert, Josh Allen."

It's a bold statement, considering Burrow's only played in 26 regular season games in his career ... but T.J. tells us he's seen enough already to put him ahead of the G.O.A.T.

In fact, Houshmandzadeh said there's a chance Burrow could be as high as No. 3 on his QB list -- ahead of Allen and Herbert.

That all being said, T.J. is entering this season with cautious optimism for his former squad -- saying anything can happen in the NFL.

"I remember playing 2006 we had a really good year and we were all extremely young and then 2007, we were ass," the 44-year-old said. "And so, I would assume they're not going to do what we did. I'd expect the Bengals for the next six, seven years to always be in contention -- but it's not going to be easy."