Barbora Krejcikova criticised a journalist's "unprofessional commentary" after he made a remark about her appearance on air.
During a Tennis Channel broadcast on Friday, Jon Wertheim commented on the Czech world number 13's forehead.
Wimbledon champion Krejcikova was competing at the WTA Finals in Riyadh, Saudi Arabia, where she was knocked out in the semi-finals by eventual runner-up Zheng Qinwen.
Wertheim said his comments were "deeply regrettable" and that he apologised to Krejcikova.
"You might have heard about the recent comments made on Tennis Channel during the WTA Finals coverage that focused on my appearance rather than my performance," 28-year-old Krejcikova posted on X.