Deontay Wilder -- I'll Fight Shannon Briggs ... But He Needs Practice!

Boxing stud Deontay Wilder -- the reigning WBC heavyweight champion -- says he's ready and willing to fight Shannon Briggs ... but says the guy needs to PROVE himself before he steps in the ring.

Wilder and Briggs -- a FORMER 2-time heavyweight champ -- went ballistic on each other during a boxing event in NYC on Friday. And now, Wilder says he's ready to back up his smack talk.

"If he wants to fight me, I'll fight. Enough talking," Wilder tells TMZ Sports ... "But he needs to get some fights under his belt first and get back into the top 15."

Briggs has been gunning for a fight with Wladimir Klitschko ... but now it seems he may have a new target.