Warren Moon Sees 49ers, Colts & Jets As Frontrunners For Deshaun Watson

San Francisco, New York and Indianapolis get excited ... Warren Moon tells TMZ Sports he believes the 49ers, Jets and Colts are the frontrunners to land Deshaun Watson!!!

The Texans QB officially wants out of Houston ... according to multiple reports, the 25-year-old is done with the team after feuding with execs, and has demanded a trade.

It's unclear if the Texans will give into the request -- considering, you know, the QB is awesome -- but if they do, Moon says he believes the Jets, Colts and 49ers are the most likely trade partners.

As for why, Moon says with the Niners, Watson could be a big upgrade if the team moves on from Jimmy Garoppolo.

With the Colts -- Moon says replacing Philip Rivers with Watson is a no-brainer ... though he wonders if the Texans would be open to an inter-division trade.

As for the Jets, Moon tells us Watson would fit in great there ... given the New York media market and the promise of new head coach Robert Saleh.

(We know Brandon Marshall certainly agrees with that one!!!)

Moon says he's hopeful that once a trade is completed, Houston will learn from this and realize if it gets another star QB, it needs to build around him and make him the team's centerpiece right away.

"Hopefully the organization will get a hint from this that we've got to do a better job going forward," Moon says. "We've got to go out and look for another top-flight quarterback and we've got to build a team around that guy so we don't end up losing him the next time."