World number one Caroline Wozniacki has complained about Monica Niculescu's "disturbing" grunting after beating her in the third round at the Qatar Open.
The Australian Open champion won 7-5 6-1 but accused the Romanian of making too much noise and spoke to the umpire.
Wozniacki, 27, continued her criticism off-court, calling Niculescu "a player that tries to get into your head".
The WTA has said umpires can act on grunting if it is deemed to affect an opponent through a 'deliberate act'.
"I just tried to let him [the umpire] know to pay attention to her grunting because she'll hit the ball and two seconds later when the ball is on my side and I'm right about to hit, she'll start grunting and make a noise, and she'll change the grunt according to what she feels like," Wozniacki claimed.