Manchester United 2-2 Porto

Nemanja Vidic says Manchester United's once-invincible defence is crumbling after the 2-2 Champions League draw against Porto and warned it must be fixed quickly.

United's back four were hailed as the best in the world when goalkeeper Edwin van der Sar went a record 1,311 minutes in the Premier League without conceding a goal earlier in the season. But not any more.

The way Mariano Gonzalez sneaked in unmarked to score a late equaliser at Old Trafford last night typified how Sir Alex Ferguson's side have struggled lately.

It wiped out Carlos Tevez's 85th-minute goal that had looked set to win the quarter-final first-leg tie despite a nervous display in which Porto went ahead after four minutes only for Wayne Rooney to equalise.

United have now conceded 10 goals in their last four matches, including a 4-1 defeat at home to Liverpool, and Vidic says the situation cannot continue.

The Serbian, who partnered Jonny Evans in the continued absence of Rio Ferdinand through injury, said: "It's very disappointing to lose a goal at the end like that when you are winning 2-1.

"If you look at the last four games then obviously we haven't played like we did in the 10 games before that. We have conceded too many.

"So definitely we need to get back on the right road and we need to get back that mentality. I don't think it's a case of players not having the confidence but maybe we've had so many games and also we've had players injured - at this stage of the season you need all your big players to be ready.

"After the Liverpool game we said we had to fix it but we didn't. Now we have to put it right."

Porto went ahead after four minutes through Cristian Rodriguez when both Cristiano Ronaldo and Evans gave the ball away. And although United equalised through Rooney, it was the Portuguese who dominated.