'I don't know': Maurizio Sarri stumped at reports Cristiano Ronaldo left stadium early after being substituted in Juventus win over AC Milan

Ronaldo looked less than impressed as he trudged off the pitch to be replaced by match-winner Dybala

Juventus forward Cristiano Ronaldo in action against AC Milan at the Allianz Stadium in Turin. AFP

Juventus' Cristiano Ronaldo and AC Milan defender Theo Hernandez go for a header. AFP

Juventus forward Cristiano Ronaldo in action against AC Milan at the Allianz Stadium in Turin. AFP

Cristiano Ronaldo runs with the ball. AFP

Cristiano Ronaldo reacts to a missed chance. AFP

Cristiano Ronaldo leaves the pitch after being substituted for Paulo Dybala. AFP

Juventus' Portuguese forward Cristiano Ronaldo leaves the pitch. AFP

Cristiano Ronaldo. Reuters

Cristiano Ronaldo leaves the pitch after being substituted for Paulo Dybala. AFP

Cristiano Ronaldo goes directly to the changing rooms. AFP

Soccer Football - Serie A - Juventus v AC Milan - Allianz Stadium, Turin, Italy - November 10, 2019 Juventus' Paulo Dybala in action REUTERS/Massimo Pinca

epa07986985 Juventus' Paulo Dybala (2-L) celebrates with teammates after scoring the 1-0 lead during the Italian Serie A soccer match between Juventus FC and AC Milan in Turin, Italy, 10 November 2019. EPA/ALESSANDRO DI MARCO

epa07987024 Juventus' Paulo Dybala (R) celebrates after scoring the 1-0 lead during the Italian Serie A soccer match between Juventus FC and AC Milan in Turin, Italy, 10 November 2019. EPA/ALESSANDRO DI MARCO

epa07987033 Juventus' Paulo Dybala (L) reacts next to teammate Gonzalo Higuain (R) after scoring the 1-0 lead during the Italian Serie A soccer match between Juventus FC and AC Milan in Turin, Italy, 10 November 2019. EPA/ALESSANDRO DI MARCO

Maurizio Sarri said he was unaware of reports that Cristiano Ronaldo left the Allianz Stadium before the end of Juventus' 1-0 win over AC Milan after being substituted for the second match in a week.

Paulo Dybala came on for Ronaldo on 55 minutes and it was the Argentina international's goal that settled the tie to see Juve leapfrog Inter Milan, who beat Verona 2-1 on Saturday, at the top of Serie A.

Ronaldo looked less than impressed as he trudged off the pitch to be replaced, and directed words at his manager Sarri before heading down the tunnel to the changing rooms.

Sky Sport Italia reported that the 34-year-old Portugal striker had left the stadium three minutes before the final whistle.

When asked in his post-match interview if he was aware of reports that Ronaldo had left the stadium, and whether that had shown a lack of respect to his teammates, Sarri responded: "Disrespectful to his teammates? Like I said, I don't know.

"If it's true that he left before the end it is a problem to be resolved with his teammates."

Ronaldo had reacted furiously after been substituted in his team's 2-1 win against Lokomotiv Moscow midweek which saw Juventus advance to the Champions League last 16.

"I have no problem with Cristiano, he should be thanked because he made himself available despite not being in the best condition," Sarri added.

"In the last month he has had discomfort in his knee and this is a little problem for him."

The win maintained Juve's unbeaten start in Serie A with the perennial Italian champions having won 10 and drawn two to move a point ahead of Inter on 32 points.

Sarri said he was unperturbed by Ronaldo's reaction to being substituted, saying he would be more concerned if his players were not upset at being taken off.

"The important thing is that he made himself available. If he gets angry when he comes out this is part of the game," Sarri said.

"It's only natural a player is going to be irritated about leaving the pitch, especially when he worked so hard to be there.

"All players who are trying to give their best will have at least five minutes of being annoyed when they are substituted, but a coach would in general be much more worried if he didn't seem upset."

Wojciech Szczesny was kept busy in the Juventus goal, denying fellow Pole Krzysztof Piatek, Lucas Paqueta and Hakan Calhanoglu as Milan belied their lowly position of 13th in the table.

Douglas Costa also came on for Federico Bernardeschi after an hour, and along with Dybala, the two substitutions changing the game for the champions.

Gonzalo Higuain fed Dybala, who easily shook off Alessio Romagnoli to beat Gianluigi Donnarumma on 77 minutes for his third league goal this season.

Lazio and Cagliari moved into the Champions League places on the back of goal-packed wins.

Lazio saw off newly-promoted Lecce 4-2, while surprise package Cagliari continued their superb form with a 5-2 rout of Fiorentina.

Lazio's Argentine forward Joaquin Correa hit a brace either side of Sergej Milinkovic-Savic's strike, with Serie A top-scorer Ciro Immobile slotting in a penalty at the Stadio Olimpico.

Belgium midfielder Radja Nainggolan contributed with three assists and capped a stellar performance with the fifth goal of the game on 65 minutes.