Ex-NFL QB Shaun King -- Warren Sapp's a GREAT Tipper ... As Long As Service is Good

Warren Sapp isn't a deadbeat diner and tips his tail off for good service ... that's according to former teammate Shaun King who tells TMZ Sports Warren is getting a bad rap in the tip-gate fiasco.

We spoke to King, who played with Sapp on the Tampa Bay Buccaneers from 1999 to 2003 and he tells us Warren is an A+ gratuity giver -- as long as the service is up to par.

"Hell Yeah he's a good tipper ... if he didn't tip [his waitress in Florida] it was something to do with the service he got."

King is also PISSED at the waitress for posting Sapp's bill on Twitter to begin with -- saying, "I have a problem with posting bills online anyway, that sh*t has the last 4 numbers of his Visa card on it and everything!"