Cristiano Ronaldo
Cristiano Ronaldo was distraught by receiving his first red card in the Champions League. In this picture, Ronaldo reacts after receiving a red card during the UEFA Champions League group H football match between Valencia CF and Juventus FC at the Mestalla stadium in Valencia, Sept. 19, 2018. JOSE JORDAN/AFP/Getty Images

Cristiano Ronaldo's reaction to his red card against Valencia on Wednesday has drawn comparisons with Serena Williams and her umpire spat at the US Open final earlier this month.

Ronaldo appeared to pull the hair of Valencia defender Jeison Murillo in the first half and was sent off for the first time in his Champions League career. The Portugal captain did not take it lightly as he heavily protested before shedding tears and leaving the pitch.

Juventus would go on to win the match regardless as two penalties from Miralem Pjanic saw them get their European campaign off to a winning start with a 2-0 victory. Ronaldo, meanwhile, will be suspended for one game at the least and miss out against BSC Young Boys, though it could be increased to three which would see him miss the double-header against his old team Manchester United.

"It was a soft sending-off for Ronaldo, but the letter of the law says you probably cannot do that, so I think the one-match ban will probably stick," former Manchester United player Darren Fletcher told BBC Radio 5 live. "He will feel like he was letting his team-mates down in that moment, but I expect him to play in both games against Manchester United."

Ronaldo's reaction went viral as many on social media compared it to how Williams protested against umpire Carlos Ramos during the US Open women's singles final, each for their own agenda though.

Ramos gave Williams three violations during the second set of her 2-6, 4-6 loss to Naomi Osaka, the first one after the American's coach Patrick Mouratoglou (admittedly) attempted to coach her from the stands.

Williams vehemently denied this and after breaking her racquet in frustration later on, was given another violation along with a point penalty. She then shed tears, claiming she would never cheat and demanded an apology from Ramos.

Her third violation, along with a game penalty, came when she started verbally abusing Ramos, calling him a thief and liar, as well as claiming he would never umpire her matches again. After the game, she also accused him of sexism, citing how male players have gotten away with worse.

Though most tennis fans felt Ramos was simply doing his job and not being sexist, the incident has stirred a debate, much like how many are debating whether Ronaldo's red card was a punishable offense.

Here is how social media compared the two incidents:

Williams has not publicly commented on the spat since US Open final but will give her full opinion in an interview with "The Project" that is set to be released this Sunday.

In a preview of the interview, she reiterated she received no coaching from Mouratoglou, while also speaking about sexism in tennis.

"He (Mouratoglou) said he made a motion. I don’t understand what he was talking about. We’ve never had signals," Williams said. "I just don’t understand. If you’re a female you should be able to do even half of what a guy can do."