Was it a foul, or wasn't it? What is the point of VAR? And if a foul is committed on Pepe, does it even count as a foul?
Costa went toe-to-toe with his former Madrid derby foe, now at Besiktas, and appeared to shove the veteran defender in the face before shimmying and shooting home to make it 1-1.
Opinion was divided on the goal, with some questioning the purpose of a Video Assistant Referee while others saw a perfectly valid goal.
Take a look at some of the best reactions to Costa's controversial strike and let us know what you think!
What’s the point if VAR if Diego Costa gets away with an albow to the face of Pepe and then scores?— Peter Schmeichel (@Pschmeichel1) 15 de junio de 2018
Unreal Diego Costa. Pure muscle. Only had to punch Pepe in the face to get there.— Kiyan Sobhani (@KiyanSo) 15 de junio de 2018
And Diego Costa just did a Pepe on Pepe— Pangeran ⚜ (@pangeransiahaan) 15 de junio de 2018
Diego Costa hitting Pepe is extremely nice and pleasing.— Diana Kristinne (@DianaKristinne) 15 de junio de 2018
Diego Costa murdered Pepe in cold blood and we all looked the other way.— Andres Cordero (@DreCordero) 15 de junio de 2018
VAR also took barely any time. Throw-ins and free-kicks both take an average of around 9 minutes each game. Worth a few seconds to eliminate absolute howlers.— Gary Lineker (@GaryLineker) 15 de junio de 2018