Paulo Dybala Photo: IC

Juventus stayed top of Serie A with a 1-0 win over AC Milan thanks to Paulo Dybala's fine strike on Sunday after Cristiano Ronaldo was substituted for the second game in a row and walked straight down the tunnel, clearly unhappy at the decision.

Ronaldo's replacement Dybala scored in the 77th minute with a goal the Portuguese would have been proud of. ­After a quick exchange of passes, the Argentine twisted past Alessio Romagnoli and beat Gianluigi Donnarumma with a right foot shot.

Ronaldo was taken off in the 55th minute, his earliest substitution since he joined Juve at the start of last season and the first time he has been replaced twice in succession.

Despite producing a lackluster display, Ronaldo gave coach Maurizio Sarri a dirty look, muttered something under his breath and walked straight down the tunnel.

Ronaldo also looked unhappy after being taken off during Wednesday's Champions League match at Lokomotiv Moscow, although Sarri said it was to avoid risking injury as the 34-year-old had complained of knee and thigh problems.

Gazzetta dello Sport said Ronaldo left the stadium before the final whistle but Sarri denied there was a rift with the five-time World Player of the Year.

"There is no problem with Cristiano, and I thank him because he has played while not in perfect condition," he told reporters.

Juventus, chasing a ninth straight Serie A title and unbeaten in all competitions under Sarri, who took over before the season started, moved to 32 points, a point ahead of Inter Milan who went top after a 2-1 home win over Verona on Saturday.

Milan's problems continued as they were left down in 14th place on 13 points after their ninth successive away defeat to Juve in Serie A.

But they gave an improved performance and had the better chances in the first half.

Misfiring striker Krzysztof Piatek headed wide from an unmarked position and Lucas Paqueta's looping header forced Wojciech Szczesny into a difficult save. Hakan Calhanoglu also tested Szczesny in the second half with a free kick before Dybala's moment of brilliance settled the match. The Argentine nearly struck again in stoppage time but was denied by Donnarumma.