MILAN (AFP) - AC Milan coach Massimiliano Allegri has demanded improvements after what he labelled an "embarrassing" last half hour in a stunning 2-0 home defeat by Fiorentina on Saturday.

Milan face Barcelona in the Champions League on Wednesday, two weeks after a 1-1 draw at the San Siro gave the Italians a share of the points and a two-point lead on Group H qualification rivals Celtic.

But in the Italian Serie A, the Rossoneri are in crisis mode.

Milan had no reply to Juan Vargas' deflected free kick in the 27th minute and when Borja Valero struck for Fiorentina in the 73rd minute, the writing was on the wall.

Milan's fifth reverse in 11 games has left them in 10th place, 18 points behind Roma ahead of the league leaders' trip to Torino later on Sunday.

Allegri, who won the 2011 league title with Milan in his first season in charge before seeing a host of established stars quit the club, has ordered his squad to retreat to the club's Milanello training base in the lead-up to Wednesday's clash.

"We have to do better and find a solution to this situation," Allegri said.

"The last half hour was embarrassing. It was the worst in my three-and-a-half years at the club."

Milan's retreat will be their second inside a month and while Allegri insisted the decision was "taken by everyone", he hopes "it will help us psychologically" ahead of away fixtures at Barcelona and Chievo, next weekend.

"We will all be at Milanello as of tomorrow (Sunday) to find a solution in this difficult moment," he added.