Cristiano Ronaldo left the Juventus Stadium before the final whistle against Milan, as he seemed irritated after his substitution.
The Rossoneri had the best chances, but when Paulo Dybala replaced Ronaldo on 55 minutes, it made the difference and La Joya scored the winning goal.
Ronaldo seemed visibly irritated at the decision, turned to mutter something in Portuguese at coach Maurizio Sarri and then walked straight down the tunnel.
Sky Sport Italia report CR7 then left the stadium before the game had even concluded, to be precise three minutes before the end of their 1-0 victory.
Sarri has said Ronaldo is struggling with a recurring knee injury, which is causing him to change his posture and running style, over-compensating and putting extra pressure on the thigh muscles.
Ronaldo had also been substituted against Lokomotiv Moscow midweek.