Woods hit the course yesterday with two male companions and practiced his ass off from 8:30 AM to 5:00 PM — working on everything from drives to pitches and putts.

We’re told Tiger’s session was uninterrupted — and he seemed completely focused throughout the entire grueling workout.

As we previously reported, sources in Isleworth tell us Tiger is dead set on competing for the Tavistock Cup — which will be held at the same Isleworth golf course where he’s practicing.

And with that news … Phil Mickelson probably needs a fresh pair of undies.

Also On 101.1 The Wiz: