Striker Victor Osimhen will "100%" be available for Napoli's Champions League quarterfinal second leg against AC Milan next week, manager Luciano Spalletti has declared.

The 24-year-old, who leads the Serie A charts with 21 goals this season, has been suffering from a groin injury and was absent from Napoli's squad as they lost 1-0 to Milan in the first leg of their all-Italian quarterfinal at the San Siro on Wednesday.

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But Spalletti insisted that Osimhen, who has also scored four goals in five Champions League games to help Napoli to reach the quarterfinals for the first time, will be back to help his team attempt to overturn their deficit.

"Victor Osimhen will 100% be available for the return leg at Maradona on Tuesday. He will be there," Spalletti said.

Without Osimhen, Napoli had more shots and more efforts on target than their opponents but couldn't find a way past Milan's defence.

After going behind to Ismael Bennacer's 40th-minute goal, Napoli's situation worsened in the 74th minute when midfielder Andre-Frank Zambo Anguissa received a second yellow card for pushing Theo Hernandez. Both he and defender Kim Min-Jae, who received a late yellow card, will now be suspended for the second leg.

"Any absence is damaging at this stage of the season, but we also have players who can fill in, which is why we are where we are. We trust the squad. We are sad not to have Anguissa, as it feels unjust not to have him, but there's nothing we can do," Spalletti said to Sky Sport Italia.

"We were on the verge of substituting Anguissa when it happened, so that is disappointing that it took us a minute or two to think of who to replace and I wasn't paying enough attention to the referee. I don't comment on the referee, that is not my role."

Napoli midfielder Eljif Elmas was more willing to comment on the performance of referee Istvan Kovacs, though, suggesting it contributed to his team's downfall.

"I don't know what to say about the refereeing, it was something incredible," he said. "He booked all our players, they committed the same type of fouls but didn't get yellow cards.

"It's something I've never seen before. It was also because of that that at a certain point we became nervous on the field."

Information from the Associated Press and Reuters was used in this report.