Jameis Winston Gets Boxing Lesson From Keith Thurman, 'Step Twist!'

Jameis Winston is adding yet another sport to his training arsenal ... this time it's boxing -- and the NFL QB is doing it with a personal punching lesson from Keith Thurman!!!

The new Saints quarterback hit up the legendary St. Pete Boxing Club in St. Petersburg, Fla. on Thursday to get in a boxing sesh with One Time -- and the vid of the training is pretty intense.

Thurman showed Jameis how to throw punches with knockout power ... and by the end of it -- the former No. 1 overall pick looked all right hitting the heavy bag!!

Of course, Winston is used to being a multi-sport athlete -- he used to pitch for Florida State while he was a superstar QB there -- so it ain't exactly a surprise to see him take the training so quickly.

As for Jameis' workout regimen this offseason ... the 26-year-old has done it all -- from pushing cars, to swinging baseball bats to dodging heavy bags being thrown at his head.