MILAN -- Victor Osimhen is out of Napoli's Champions League quarterfinal first leg against AC Milan after failing to overcome a groin injury in time to play in the San Siro on Wednesday.

The 24-year-old, who leads the Serie A charts with 21 goals this season, was omitted from Luciano Spalletti's squad for the trip to Milan and is now battling to prove his fitness for the second leg in Naples on April 18.

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But Spalletti said his team are capable of taking control of the tie without the star striker and urged them to treat the occasion as being "like Christmas Eve."

"I decided not to play Osimhen because I don't want him injured for too long," Spalletti said Tuesday. "We have another game against Milan next week and I want him fit for that.

"But we have won very important games without Osimhen. We are here because we have won without him in this competition and I am expecting the same, that all my players rely on their teammates' abilities.

"We can't go on the pitch and be afraid. We need to take this chance and enjoy the game.

"This is like Christmas Eve. The game, the day before the match, the dinner before the match, it is all there to be enjoyed."

The absence of Osimhen, who has scored four goals in five Champions League games this season, is a major blow to Napoli, who had gone into the tie as favourites having built a 16-point lead at the top of Serie A. Spalletti's team, aiming to win the scudetto for the first time since 1990, are 22 points clear of fourth-place Milan.

The Nigeria international has been absent since scoring twice against Torino on March 19, missing Napoli's past two games, including a 4-0 defeat at home to Milan on April 2, and had been regarded as in doubt for the first leg.

Despite Osimhen's failure to earn a place in Spalletti's squad, Napoli captain Giovanni Di Lorenzo said his team can overcome the loss of their "crucial" centre-forward.

"We can loudly say that he [Osimhen] is fundamental for the team," Di Lorenzo said. "He is crucial, but we don't just rely on Osimhen. We rely on all of our teammates.

"We are calm and relaxed because we have to face this battle with the players who are available. Osimhen is injured, we can't run the risk of him playing and being injured for another five games.

"All of our players can score and that is very important for the team, especially in a game as difficult as the one we face tomorrow. We have to take every chance that we get.

"It will be a whole different story this time [than the 4-0 defeat against Milan]. The Napoli you saw against Milan last week is not the Napoli that you normally see. This is Champions League, not Serie A, and our attitude will be different."