Manchester United may have played like novices in Europe in midweek but they are seasoned hands when it comes to the Premiership and yesterday they did what they do best: dispose of a team high in ambition but too low to be part of the domestic élite.
In theory Birmingham, undefeated and in fourth place, should have given the champions a demanding test, but United dealt with them with ease. True, they were assisted by the sending-off of the visitors' goalkeeper, Maik Taylor, but determined and hard-working though Steve Bruce's team were, the red card served only as an invitation to the inevitable.
Beforehand the Birmingham manager had picked Paul Scholes as United's greatest threat and, with the prescience he often showed when he was a tower guarding the Old Trafford citadel, he was proved right. The England midfielder gave a virtuoso performance drifting between midfield and attack, finding space at will.
It was Scholes who was brought down for the penalty that led to Taylor's sending-off and Ruud Van Nistelrooy's ninth goal of the season, and he got the second that put the game beyond Birmingham's grasp. By the time Ryan Giggs scored with nine minutes left the mood had been reduced to practice match proportions.
"The turning point was the penalty," Bruce said. "And we were punished three times, through the penalty, going down to 10 men and now losing Maik for the derby game against Aston Villa.
"You would think the penalty was punishment enough but the referee has to follow the letter of the law or he is marked down by his assessors. The common sense element the referee used to have is not there any more."
Sir Alex Ferguson, the United manager, agreed. "The goalkeeper had to go for that ball," he said. "It was a beautiful pass from Ruud and Scholes had to take him on because the goalkeeper came out so quickly."
United began under the shadow of their 2-1 Champions' League defeat to Stuttgart. Ferguson said their defence there was "terrible", and perhaps all the talk of defence influenced this game because for the first half hour there was barely an attacking move of note. Indeed, if Scholes had not fired in a header and a highly stoppable shot in the 16th and 17th minutes the goalkeepers would have been entirely redundant. Which was ironic because Taylor was out of the game after 33 minutes.
One of the more underrated aspects of Van Nistelrooy's play is his ability to bring other players into moves and it was his exquisite turn and pass that pushed Scholes beyond the Birmingham rearguard. Scholes won the race to the ball and when Taylor crashed into him the referee had little option but to award a penalty and to dismiss the goalkeeper.
Birmingham brought on Ian Bennett but the substitute goalkeeper had little chance of stopping Van Nistelrooy's spot kick, diving to his right as the Dutchman, who has missed three penalties this season, calmly shot into the alternate corner.
Birmingham were a man down but had the wind in their favour in the second half and nearly equalised within two minutes of the restart. Rio Ferdinand and Mikaël Silvestre did not tackle Mikael Forssell with conviction and the ball slipped out to Jamie Clapham, who tried to bend his shot but hit the advancing Tim Howard.
You do not get many chances to embarrass United at Old Trafford and after 56 minutes that opportunity disappeared. The home team's passing had been far from a thing of beauty, so it was surprising that they made a move of genuine craft, Darren Fletcher heading down for Gary Neville to play to Scholes. Birmingham had been confused by his running all afternoon and this time they watched as he thumped a low shot into the net.
Diego Forlan was introduced after 65 minutes to rest Roy Keane and it was the Uruguayan who made United's third goal, cutting in from the left and waiting until the right moment to deliver his pass. One on one with Bennett, Giggs slipped the ball past the goalkeeper with ease.
Manchester United 3 Birmingham City 0
Van Nistelrooy pen 36, Scholes 57, Giggs 82
Half-time: 1-0 Attendance: 67,633