ROME — Italy forward Simone Zaza injured his left knee in training on Thursday, a day before the first leg of a World Cup playoff against Sweden.

The Italian soccer federation said Zaza stopped training because of a “flare-up of a previous problem with his left knee.”

Zaza travelled with the rest of the squad to Sweden but is in doubt for Friday’s match.

There are already question marks over forwards Andrea Belotti and Ciro Immobile. Belotti, who scored 26 goals with Torino in Serie A last season, is working his way back from a right knee injury. Immobile leads the Italian league with 14 goals in 11 matches this season but recently strained a leg muscle.

“Zaza had a slight problem, but we are not going to despair,” Italy coach Gian Piero Ventura told a news conference at the stadium in Solna. “If he is fit he’ll play, if not we’ll try to get him ready for Monday.

“Belotti is much better now than when he arrived, he had only played two games with little training since the injury, so he wasn’t at his best.”

The two teams meet in the opening leg on Friday, in one of four European playoffs. The return match will be at the San Siro in Milan three days later.