Tomic can't keep his mouth shut

Fiery Australian star Bernard Tomic was at the center of a foul-mouthed US Open controversy on Tuesday when he became embroiled in a lewd exchange with a heckler.

The 23-year-old slumped to a 6-4, 6-3, 4-6, 7-6 (7/0) loss to Damir Dzumhur of Bosnia on the old Grandstand court.

But before he lost the first round match, he also spectacularly lost his composure, angrily barking back at a spectator he accused of deliberately trying to get under his skin.