Frances Tiafoe absolutely lost it on an umpire on Tuesday ... cussing up a storm as he expressed his frustrations over a controversial call.
The tennis star lashed out following his loss to Roman Safiullin at the Shanghai Masters ... clearly pissed off about how things unfolded earlier in the match.
During the contest, the umpire gave 13th-seed Tiafoe two time violations ... the second one taking away Tiafoe's first serve on a crucial point in the tiebreaker.