MILAN – Cristiano Ronaldo made his home debut for Juventus, missed an open goal but unintentionally offered Mario Mandzukic a chance to score when the Serie A-title-sitters defeated Serie 2 on Saturday-2-0.

Juventus, chasing an eighth consecutive title, have six points from two games after a somewhat fortunate victory, but Ronaldo is still waiting for his first goal since his move from Real Madrid.

Piotr Zielinski scored twice, as Napoli scored two goals and beat AC Milan 3-2 and gave new coach Carlo Ancelotti an unforgettable home debut, especially as it came to the side where he spent eight seasons of his coaching career.

Striker Gonzalo Higuain also made his debut for AC Milan after his loan from Juventus, but he had little impact.

Miralem Pjanic threw Juventus in the 30th minute with a shot from outside the area before the Turin added a sloppy second score in the 75th minute.

Joao Cancelo's low pass was partially intercepted by Lazio goalkeeper Thomas Strakosha, but his shot went just wide.

The Portuguese turned the ball towards goal with his right foot, but his left heel blocked the shot and the ball rebounded on the path of the Croatian World Cup forward, Mandzukic, who threw it home.

The nearest Ronaldo came to break his duck was with a vicious dipping attempt on the turn in the 71st minute, but it was brilliantly flipped through the bar by the Albanian goalkeeper.

Juventus goalkeeper Wojciech Szczesny, again giving preference to the new signing Mattia Perin, made two important rescues in the first half, which turned Senad Lulic's shot and overturned his goal to prevent a dangerous break by Marco Parolo.

"Italian football is completely different from Spain, Ronaldo understands that and he is doing well," said Juventus coach Massimiliano Allegri.

"There was a risk that we would get carried away by the enthusiasm of Ronaldo's first house," added the coach, who selected Blaise Matuidi and Federico Bernardeschi for Paulo Dybala and Juan Cuadrado.

"I have a very strong team and have to evaluate everyone, and we needed these features today in the midfield," he said. "There are times when we are too busy and other times when we go to sleep, and we need a better balance."

AC Milan stunned the San Paolo when Giacomo Bonaventura's unorthodox salvo put them ahead in the 15th minute and Davide Calabria drove in the second of Suso's clever resignation four minutes after halftime.

Zielinski retreated three minutes later and rolled the ball into the far corner from the edge of the area after Milan had lost its own half, and from that moment on a Napoli battle-back seemed to be on the cards.

The Pole drove home the equalizer in the 67th minute after attempting Milan from the corner of a corner landed at his feet and substitute Dries Mertens completed the job with another 10 minutes to go, turning in Allan's low cross on the other post.

There was a big cheering voice shortly afterwards when Higuain shot high and wide from his only real opening of the game.

The victory left Napoli, the second place last season under Maurizio Sarri, with six points from their first two games.