MILAN, Sept. 30 (Xinhua) -- AC Milan head coach Massimiliano Allegri said on Monday that his side could face Barcelona with calm provided they beat Ajax in the Tuesday's Europe Champions League group match.

The Rossoneri have traveled to Amsterdam for their second Champions League group stage match of the season, and Allegri said this match could be crucial for their showdown with Barcelona.

"If we win it would be a big step forward for us, and would allow us to go into the double challenge of Barcelona with some calm," he said. "We know though that we're going to have to play well."

The Milan side will face Ajax without the service of injured Stephan El Shaarawy.

"Yesterday Stephan took a knock in training and felt some pain, " Allegri said. "As a precaution we sent him for a scan, and there it was revealed that he has suffered a microfracture which will keep him out for 20-30 days."

"It's a shame because he was back in form after a muscle problem and we were counting on him for this match. Tomorrow we' ll have Balotelli back, but I think his recent suspension has shown him that he has to change his attitude on the pitch," he said.

He warned his players against underestimating Ajax.

"In Europe there are no easy games. Ajax play some good football and have a great tradition. We'll need to be very careful," he said.