Twelve months ago, the task proved beyond Sir Alex Ferguson’s men at the Stadium of Light. This time around, the demand is slightly easier courtesy of home advantage and the knowledge a draw will be enough to squeeze the Red Devils into the last 16.

But against a Benfica side who have started to hit form and who know victory is a must for their own qualification hopes, nothing can be taken for granted on December 6.

“We only have ourselves to blame,” said Giggs.

“We had a lot of the ball and we had the chances. Celtic hardly got our of their own half in the first half.

“But when you are on top, you have to take your opportunities and we did not do that. Now we have to play Benfica again.

“It won’t be easy, we are aware of that. But maybe one thing in our favour is that we know Benfica have to win, so they will have to come out and attack us.

“But we are at home and we know what we have to do. Hopefully we can.”

Sir Alex Ferguson’s bullish post-match confidence that his team will go through is based on an impressive European record at Old Trafford.

The last time United lost a group stage tie on home soil was against Deportivo La Coruna in October 2001.

However, they were beaten at home by AC Milan in the knock-out phase two years ago and it was their failure to overcome Jose Mourinho’s FC Porto at Old Trafford which led to their elimination the season before.

By the time Benfica arrive in Manchester, United will almost certainly have a new penalty-taker.

Given the startling assertion of Gary Neville that Louis Saha’s “head had gone” before he failed to beat Artur Boruc with his last-minute spot-kick at Parkhead, it is a wonder the Frenchman was given the responsibility at all.

Saha had only just spurned a gilt-edged opportunity when he latched onto Wayne Rooney’s chipped pass and lamely chipped into Boruc’s arms, clearly believing he was offside, when in fact play had been waved on.

“Louis thought he heard a whistle,” lamented Ferguson.

Either Rooney or Cristiano Ronaldo should now assume spot-kick duties, although Giggs is eager not to apportion too much blame to Saha for the miss, which could cost United a place in the knock-out stage with a game to spare.

“It was unfortunate for Louis but we should have had the game wrapped up long before then anyway,” said the veteran Welshman, who played his part in what was a thoroughly dominant and effective performance before Shunsuke Nakamura curled home his magnificent winner.

If last night’s return to his native city represented one of those occasions when Ferguson saw his team do everything but gain the victory their play deserved, how the Scot must regret United’s failure to at least get a point from last month’s visit to FC Copenhagen.

Instead of being able to stroll into the next stage, the Red Devils instead found themselves pitched into a full-throttle ‘Battle of Britain’ clash and are now facing up to the prospect of another do-or-die encounter on the European front at a time when the Premiership programme is at its most intense.

Manchester City – a side United have beaten in league combat only once in five attempts on home soil – follow Benfica to Old Trafford, while Ferguson’s men now have just four days to limber up for their crunch clash with Chelsea.

“We have to get some rest over the next couple of days and make sure we are ready for Sunday,” said Giggs.

“That is a massive game for us now.”