Juan Cuadrado helped Juventus open up a four-point lead at the top of Serie A with a goal against AC Milan on his comeback, but the winger warned the title race is not done yet.

On a huge day in the battle for the Scudetto, Napoli squandered the chance to temporarily move ahead of Juve by drawing 1-1 at Sassuolo, with the Bianconeri then overcoming Milan 3-1 later in the day to increase their advantage.

Though Juventus led through Paulo Dybala's strike from range, their former defender Leonardo Bonucci levelled for Milan, who were then on top and hit the crossbar through Hakan Calhanoglu.

Yet Cuadrado, who came off the bench for his first appearance of 2018, headed in Sami Khedira's cross to put Juve back ahead before Khedira himself then scored a third to give Massimiliano Allegri's men a huge victory.

Juan Cuadrado and Juventus are four points clear at the top. EPA/ALESSANDRO DI MARCO

"Let's stay calm -- we haven't won anything yet,'' Cuadrado said in quotes published on Juventus' website. "Now we look towards Real [Madrid in the Champions League]. For now we can be really happy -- Napoli only drew so we've been able to extend the gap.

"Are we favourites? No. We need to stay calm. There's still a long way to go in the league and we need to keep doing our best in every game."

It was a similar message from Allegri as he conceded his side, who had drawn 0-0 with SPAL prior to the international break, found a way to win despite being below par for long periods.

"We've got back the lead that we had and there's now one less game left to play," Allegri said. "However, we've still got a long way to go in the league -= we cannot afford to let up, not for a single minute, because everyone's going strong.

"It was important for us to get back to winning ways and against a team in good physical shape.

"Once we went ahead we dropped off a bit and struggled to keep hold of the ball, but credit also to Milan for that. However, a result like this was important to begin this final stretch of the league campaign.

"It is important to understand moments in games and we did that, showing our desire to keep going, to go as far as we can and achieve our objectives."