Packers Star Donald Driver -- I'm Busting My Ass For 'Dancing with the Stars'

Four-time Pro Bowler and children's author Donald Driver isn't taking "Dancing with the Stars" lightly -- sources tell TMZ, the Green Bay wide receiver is working himself to the BONE to crush the competition.

According to sources, Donald's been working non-stop -- practicing with his partner for 5 hours at a time ... then going home and studying dance moves on YouTube.

We're told Donald pays especially close attention to the male pros -- intently studying their moves and their footwork ... just like a football player would study tapes of old games.

According to sources, Donald's goal is to dance at the pro level -- not just the "celebrity" level.

We're told Donald is so focused on being at the top of his game -- he's even keeping his pro partner Peta Murgatroyd on a strict diet.