Gilbert Arenas Rips Tiger Woods' DUI Excuse, 'Just Say You Got F'd Up'

Gilbert Arenas isn't buying Tiger Woods' prescription pill DUI excuse -- telling TMZ Sports, "That's the suckiest sh*t about being an athlete, you gotta lie."

The ex-NBA superstar was leaving Catch in West Hollywood (he was a passenger) -- when he told us what Tiger should have said in his statement ... instead of blaming Rx medication.

"Just say you got drunk, you got f**ked up like everyone else in America," Arenas said.

"Mixed medication, really??"

He also doesn't think the DUI charge will stick -- "As long as no one died, he should be fine."