The Scot was in the stands at Old Trafford last night as the Portuguese side snatched a deserved 2-2 draw in their Champions League quarter-final first-leg clash with United to head into the deciding 90 minutes with a marginal advantage.

Sbragia's relegation-threatened side entertain Sir Alex Ferguson's men at the Stadium of Light on Saturday desperate for something tangible to show for their efforts after slipping to within three points of the drop zone.

However, Ferguson's former reserve-team coach knows exactly what to expect from the reigning Barclays Premier League, European and World Club champions even after a run of just one win in their last four games in all competitions.

He said: "Porto surprised them. They attacked them early doors, got the goal and had a couple of chances and they made the game big as well.

"They worked extremely hard against Manchester United, but I felt the longer the game went on, Manchester United started taking charge of it.

"They got back to 2-1 and the game, for me, would have been over. But credit to Porto, they came back and scored late on.

"But they can change it around. You look at their bench last night and they have got some good players there as well who they can bring in."

Ferguson has already ruled defenders Rio Ferdinand and Jonny Evans, who enjoyed two hugely-successful loan spells on Wearside under Roy Keane, out of the game through injury, while star man Cristiano Ronaldo has looked out of sorts in recent weeks.

However, for all United were disappointed not to secure a lead to take to Portugal last night, they showed immense character to bounce back from successive league defeats by Liverpool and Fulham as they came from behind and defeated Aston Villa at the weekend.

They were trailing 2-1 with just 10 minutes remaining when Ronaldo levelled with his second of the game, but it was 17-year-old Italian Federico Macheda who snatched victory and the headlines with his first senior goal for the club in injury time.

It is that strength in depth, despite a run of, by their standards, indifferent form which Sbragia fears as United prepare for a third game in seven days.

He said: "They are a top team and we know it's going to be very difficult.

"We watched them against Porto last night and watched them against Villa, and they are a good team. They are an attacking team, they score goals.

"You just don't know what sort of team they are going to put out on Saturday, but we know it is going to be a very difficult game.

"It's typical Manchester United. They have got some excellent players and whatever players they bring into the team are going to be quality."

Sbragia has his own selection problems, many of them form-related with the Black Cats having won only one of their last eight league games.

However, he is likely to be without left-back George McCartney for several weeks because of the calf injury he suffered on international duty with Northern Ireland against Slovenia last week.

Sbragia said: "George looks as if he will probably be out for a couple of weeks. He has got a slight calf injury.

"The way he has been talking, he has felt it for the last four or five weeks, but he really pulled it in the Northern Ireland international game, so I don't think I will have George available for Saturday."