Jonny Evans has joined Manchester United's injury list after Sir Alex Ferguson predicted a difficult test away to Porto in the second leg of the UEFA Champions League quarter-finals.
United produced a sloppy display at Old Trafford to draw 2-2 after Mariano Gonzalez scored an 89th minute equaliser for Porto, who were the better team for long spells.
No English team has ever won at Porto's Estadio do Dragao ahead of the holders' trip to Portugal for the return next week.
Ferguson is aware of the history, but he is determined to steer the Red Devils through to the semi-finals of the competition.
Used to being first
"No British team has won there, so it is going to be difficult," admitted Ferguson.
"But we are used to being first and we need to be first again because we have to win."
United lost Northern Ireland defender Evans to a groin injury and he is unlikely to be fit for the Premier League trip to Sunderland on Saturday.
Rio Ferdinand missed the Porto game with a groin complaint and Ferguson does not expect the centre-half to return for the weekend.
He added: "Rio was nowhere near being fit tonight, so it is difficult to see him being fit for Saturday.
"Jonny should be okay in a week, but he is a 21-year-old lad and this is what happens when you play two big games in three days."
Substitute Carlos Tevez had given United an 85th minute lead and Ferguson was disappointed to concede such a late equaliser after Mariano was left unmarked at the far post.
"We only have ourselves to blame," said the Red Devils chief.
"To get a goal late on is quite a normal situation for us. But the one we gave away was absolutely terrible.
"You couldn't say it was a great goal or a manufactured goal, but we just made the kind of mistake we are making at the moment."