Utah Jazz center Jeff Withey says he NEVER got physical with his Playboy Playmate ex-fiancee, Kennedy Summers ... claiming she made the whole thing up to damage his reputation.

As we previously reported, Summers -- the 2014 Playmate of the Year -- filed a police report earlier this week accusing Withey of domestic violence in an alleged 2016 incident.

Now, Withey's attorney, Alan Jackson, is firing back with a very strong denial.

"These salacious and patently false allegations appear to be nothing more than a vicious and calculated attempt by an angry former girlfriend to damage Mr. Withey’s good reputation," Jackson says.

"It is no coincidence that these fabricated claims conveniently come during the middle of the NBA playoffs, or that TMZ and the police department were notified on the same day."