Milan's Champions League quarter-final opponents Barcelona lodged an official complaint with UEFA over the standard of the pitch after the goalless draw between the two sides in Wednesday's first leg.

Milan issued a statement defending the condition of the pitch but Allegri told reporters on Friday that the problem needs to be resolved.

"We have to solve the problems with the pitch at San Siro, because the pitch gets changed five to six times a year," Allegri said.

On a more positive note for Milan, Antonio Cassano, who has been out of action since undergoing an emergency heart procedure last November, is nearing a return to first-team duty.

Allegri is optimistic of having the forward at his disposal for the Serie A title run-in.

"I can't use Cassano until the doctors give him the green light," Allegri said. "But I hope that he'll be ready for the final part of the season."

Allegri is also hoping that Alexandre Pato, who has been plagued by thigh problems this season, will be available for selection again after visiting an Atlanta-based specialist this week.

"Pato will return from the USA," Allegri said. "He's feeling fine. We will evaluate his condition on Sunday to find out when he can play again."