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."
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