Stefano Pioli says Zlatan Ibrahimovic has a "fire within him" after he marked his return from injury on Sunday with a goal in Milan's 2-0 win over Lazio.

Ibrahimovic – making his return to action following a knee injury sustained in May – was introduced as a substitute in the 60th minute and wasted little time making an impact, tapping in just seven minutes later to double his side's advantage.

They had earlier gone ahead thanks to Rafael Leao's second goal of the season, while Franck Kessie saw a penalty crash back off the crossbar in first-half stoppage time.

The result means Milan have won their first three Serie A fixtures in consecutive seasons for the first time in the Italian top flight.

Ibrahimovic will turn 40 next month, but Rossoneri boss Pioli insists his age will be no barrier to him enjoying another successful season at San Siro.

"Zlatan hadn't played for four months, so I'm glad he scored a goal and will get stronger in the next games," he told DAZN.

"He has this fire within him. The way he battles in training as well as games, all aiming to be the best. You don't feel the years when you do that."

Leao has already scored a third of his Serie A tally from last season, with his strike against Lazio coming from a joint game-high three shots.

While Pioli is expecting big things from the Portuguese forward, he urged him to sharpen up on his finishing.

"Rafa was already a strength for this team last season, but he's still 22 years old. It's only his third campaign in Italy, the second working with me," he added.

"He needs to become more efficient in the finish, because he almost always gets past his defender and just has to finish off more of those chances."

There was drama at the full-time whistle when Lazio boss Maurizio Sarri was shown a red card for an altercation with Alexis Saelemaekers.

Sarri played down the incident but was clearly unhappy with the Belgium international's behaviour.  

"It was nothing in particular," Sarri said.

"The young lad made a gesture that you shouldn't do to older people and Ibrahimovic then calmed everything down. These things happen on the pitch."