Sir Alex Ferguson's 70th birthday celebrations at Old Trafford fell unexpectedly flat as Blackburn Rovers enjoyed their first away win of the season, not only preventing Manchester United overtaking Manchester City at the top of the Premier League but taking the shine off the manager's pre-match announcement that he hoped to stay on for another three years.

Ferguson has been reticent about setting a date for retirement since the events of a decade ago, when he changed his mind about retiring at the age of 60 because he felt he was still the best-qualified person to run the team. With another European Cup, five Premier League titles, an FA Cup and three Carling Cups accrued in the meantime, Ferguson probably feels just the same now, though he did acknowledge that his age was a matter of legitimate concern.

"I suppose inevitably Manchester United supporters are going to be asking whether a man of 70 is up to managing this great club," he said. "I have asked myself that, though the only answer is that proof of the pudding is in results. We have had our ups and downs in this campaign but overall the first half of the season has been as good as anything I've seen in the last 25 years. As someone who loves my job I am not about to let years alone dictate my future. At my age health becomes the key issue for a man's work and I am happy to say I have been blessed with the stamina and energy to cope with a demanding job, one that has grown enormously since I first moved down from Aberdeen."

Had Ferguson's players been able to demonstrate the same energy and stamina against Blackburn they may have enabled their manager to enjoy both his birthday and the New Year, but a lengthy injury list and a heavy pitch led to a much-changed side that went two goals behind before some of the original positional errors were corrected. With even more of the spotlight than usual trained on the Premier League's most experienced manager this was not Ferguson's finest hour. He started Antonio Valencia at right-back, with Rafael da Silva bizarrely stationed in midfield, then admitted Valencia had an excellent game when moved back to his true right-wing position for the second half. He blamed a dead, rain-soaked pitch for slowing down the game when Blackburn found the going just as heavy, and he listed United's injuries when Steve Kean's much smaller squad had just as many and were practically fielding a team of reserves and juniors.

"We never expected that," Ferguson said of the defeat. "We lost two terrible goals in the game and you can't do that when you are playing a side that's fighting for their lives. We missed the experience of Michael Carrick and Ryan Giggs in midfield, but having said that when we got back to 2-2 I was certain we would win. Valencia had a great game in the second half but we couldn't finish them off.

"We never got any breaks in the game, though I will admit we could have dealt with their winning goal better. It wasn't just the goalkeeper's fault, I thought we all could have reacted better. Obviously it's disappointing not to be able to go top but we are still in touch and that's where we wanted to be. We won't play like that too often this season, we can play a lot better."

After winning the previous four games following their Champions League exit and scoring 16 times in the process, this was a reminder, and there have been others this season, that Ferguson does not always get it completely right. He has indeed been unlucky with injuries to key players, but so has Kean. "Who would have thought at the start of the season," the Blackburn manager asked rhetorically, "that we would have to play a back four of Jason Lowe, [Chris] Samba, [Grant] Hanley and [Adam] Henley? Who would have thought that we could win at Old Trafford with a line-up like that?" The question many United fans will be asking, as they wait to see how expensive these dropped points may be, is who would have thought they would see a United back four of Valencia, Carrick, Jones and Evra?