The full impact of Manchester United's defeat to Fiorentina on Tuesday night, in their opening match of the second stage of the Champions' League, was not apparent until the post-match press conference at the Artemio Franchi Stadium. Then an Italian journalist, the bewilderment evident in his voice, said to the Fiorentina coach, Giovanni Trapattoni: "No one expected this result. How do you explain it?"

The full impact of Manchester United's defeat to Fiorentina on Tuesday night, in their opening match of the second stage of the Champions' League, was not apparent until the post-match press conference at the Artemio Franchi Stadium. Then an Italian journalist, the bewilderment evident in his voice, said to the Fiorentina coach, Giovanni Trapattoni: "No one expected this result. How do you explain it?"

How indeed. Trapattoni claimed superior tactics; Sir Alex Ferguson blamed individual errors. Both are correct. Each Fiorentina goal was the consequence of a bad mistake but United never closed down Rui Costa as effectively as the home team blocked off the holders' avenues of attack. Even United's late bombardment failed to produce much in the way of chances and Francesco Toldo was rarely tested.

Maybe it is a reaction to last season's exploits, maybe it is a hangover from the defensive problems of autumn, or just a realisation that this is going to be a very long season, but United have rarely played at their best this campaign, home or abroad.

In Europe now, as well as domestically, opponents raise their game against them - Gabriel Batistuta's work-rate was a wonder to behold on Tuesday - and they have not always responded. Last season they were unbeaten in a 13-match European campaign; this season they have lost twice in seven matches, to Marseilles and Fiorentina, and to Lazio in the European Super Cup.

Too many players are struggling to reach last season's heights, with the creative players suffering more than most. In addition Roy Keane appears distracted by the speculation surrounding his future.

Yet it is the form of Dwight Yorke which may well be worrying Sir Alex most. Unlike Andy Cole, who plays in the more advanced position and is thus dependent on good service, Yorke usually is a key figure in United's build-up play. He rarely featured on Tuesday and it was no surprise when, for the third time in five matches, he was withdrawn around the hour mark.

After starting the season with six goals in as many matches Yorke's output has dwindled to the extent that he has now scored once in 10, in the 4-1 rout of Watford at Old Trafford. On away grounds he has only scored against Sturm Graz, Coventry and Everton, reviving the old chestnut, first raised in his Aston Villa days, about his being a "home ground" player.

Though he was also quiet in the European Cup final and at Internazionale, his goals against Bayern Munich and Juventus last season, and his performances in Turin and away to Barcelona, are powerful counterpoints to that argument. More likely he is just suffering a drop in form and, consequently, confidence.

Only Jaap Stam and Phil Neville have played more than Yorke this season but it is not easy for Sir Alex to give him a break. Teddy Sheringham is not on speaking terms with Cole, and although players do not have to like each other, this cannot be healthy in a strike partnership. Perhaps because of this, Sheringham and Cole have played only 229 minutes together this season, the equivalent of about two-and-a-half matches.

Sir Alex did rest Yorke in the Super Cup match and it will be interesting to see who he plays against Palmeiras in the Intercontinental Cup, in Tokyo, next Tuesday. It is, despite the strange venue, a prestigious match.

United's only other attempt to become the World club champions, in 1969, ended in a bitter and controversial defeat to the notorious Argentinian side Estudiantes. While modern football is much cleaner, Tuesday's game also promises to be physical. Palmeiras are known for their aggressive tactics - their coach, Phil Scolari, publicly called for his players to commit more fouls last season.

Meanwhile, Florence was still celebrating yesterday. Corriere dello Sport described the match as "a lesson to Manchester" from Florence. It gave Roy Keane ("a disappointment"), David Beckham ("no sting") and Paul Scholes ("disappeared") five out of 10 - only Henning Berg got fewer points on either side. Meanwhile, Flond said Fiorentina were "in a dream", the city "wild with love" for their players. The reaction underlines the status United now hold, and the standards they have yet to live up to.

The Valencia midfielders Gerard Lopez and David Albelda are suspended for the Champions' League game against United at Old Trafford on 8 December. Both players collected their third bookings in the competition during their side's 3-0 home victory over Bordeaux on Tuesday.