Ex-Manchester United defender Paul Parker fears his former club will be made to rue their performance against Barcelona in the first leg of their Champions League semi-final tie.

"It was no surprise that the result at the Nou Camp was better than the performance. United haven't overwhelmed teams in Europe so far this season and have simply got the results they needed without really putting on a show.

United played too deep against Barcelona, although I don't believe that was a deliberate tactic on the part of Alex Ferguson. The boss knows that European games can quickly turn if you allow teams to come on to you and he knows the importance of an away goal. He wouldn't have sent his side out with such orders and United's defensive performance was down to a combination of sub-par individual showings and a decent Barca showing.

That Cristiano Ronaldo was forced to pick up the ball in midfield and run the length of the pitch all on his own to make any kind of headway into the Barca defence said a great deal. There was nobody bursting forward from midfield to support him and it all looked a bit static in the middle.

It took a few clever substitutions to turn the game in Lyon in the last 16 and we saw a bit of jiggling spark United into life against Arsenal a few weeks ago. The performance at the Nou Camp was crying out for a similar change to inject some life into the midfield - Nani or Anderson could have provided that, but Ferguson opted to bring just one of the pair on, and a little too late to change the game.

United got away with it, and a goalless draw is not a bad result.

But Barca have such quality going forward, I fear United have it all to do in the return leg. And with that goal threat, realistically United need to score at least twice at Old Trafford before they can relax.

True, Barca didn't threaten too much at the Nou Camp, but the way they played will have given them the confidence to come and play in Manchester. They are arguably the best footballing side in Europe - they keep possession better than anyone and chances will always come to those sides that retain the ball.

And it remains to be seen how the United defence will cope with an onslaught - they have not been fully tested, a few scares aside, over their last three Champions League ties. Tuesday's game will be a completely different kettle of fish.

Lionel Messi will have another game under his belt after returning from injury and Thierry Henry, if selected, still has a point to prove.

Messi was outstanding at the Nou Camp and poses a real threat to United's hopes of getting to the final. He came off because Frank Rijkaard didn't really want to be too greedy in what he was getting out of him.

In Manchester, we will see even more of his talent because he will have a bit more room to play in as United push further up the field. The game in Spain was very compact but it won't be the same on Tuesday and that will allow Messi to come into his own.

For me, the most disappointing aspect of the game was that the Barcelona defence - which had been identified as a weak link before kick-off - was never tested. Simply, United weren't brave enough to have a go.

They'll have to be a great deal more cavalier in the return leg if they are to book a date in Moscow."

Eurosport