Manchester United know all about the power of reserves when playing Bayern Munich. Two years ago in Barcelona Teddy Sheringham and Ole Gunnar Solskjaer came off the bench to give United one of the most dramatic European Cup victories in recent times.

Last night Bayern had the sweetest revenge possible, therefore, when their Brazilian substitute, Paulo Sergio, came on to give Bayern a well-deserved winner not long after another substitute, Alexander Zickler, had beaten Fabien Barthez only to see his volley canon back off the crossbar. That Paulo Sergio's effort came in the 86th minute only heightened the sense of comparison with Barcelona.

The Germans had been an increasing force in the land the longer the night went on, and they will be confident of progressing to the semi-final now. Not only did they see little to scare them here, United will be without David Beckham for the return in Munich, though whether that is a handicap remains to be seen after Beckham's erratic performance last night. Beckham was booked for a foul on Stefan Effenberg and is now suspended. His absence will be offset by Bixente Lizarazu's for Bayern.

United had started brightly but their enthusiasm gradually gave way to predictability, and if ever an occasion cried out for the larcenous skill of Sheringham to be introduced then this was it. Sheringham, however, only left the bench to have a bath.

He will need to play in Bavaria, and there is still the possibility that the tie can be recovered. Had Bayern been more composed with their finishing that would have been an impossibility. Barthez made three invaluable second-half blocks that kept United afloat, and then Zickler missed a sitter shortly after Paulo Sergio's breakthrough. Alex Ferguson looked a demoralised man after that but maintained the tie is still live. "If we can score out there it will completely change the game," he said. "But it's difficult. I thought we played well in the first half but we didn't get the supply to Cole and Solskjaer in the second."

Ferguson had caused something of a surprise with the inclusion of Solskjaer on the right and Andy Cole on his own in the middle. But there were just two opportunities in the first half, and Cole wasted the best after 16 minutes. Having been released by Beckham's cross to the far post, Cole snatched at a first-time volley. It was another 18 minutes before anything equally open was created. This time Cole did the heavy work, setting Solskjaer free with a chip over the top of a Bayern defence trying to play offside. Solskjaer bore down on Oliver Kahn, but as he steadied himself the Norwegian was closed down by a Swede, Patrik Andersson.

Other than that United were held at bay and it was the Germans who threatened. With Effenberg directing effortlessly and Mehmet Scholl roving dangerously in front of him, Bayern could have taken a 21st-minute lead when Effenberg lobbed Carsten Jancker into the United box. Jancker's control and strength were good but his shot was straight at Barthez.

That was Barthez's only early activity, but he should have been forced into more decisive action when a slick Bayern breakaway instigated by Effenberg and continued by Scholl ended with a weak defensive header from Silvestre. But Hasan Salihamidzic blasted over.

United were reacquainted with that threat immediately from the re-start. After Silvestre had wrestled Jancker to the floor on the edge of the area, Effenberg drilled in a free-kick inches over Barthez's bar. Six minutes later, yet more cohesive German passing featuring Effenberg and Scholl gave Giovane Elber the chance of a first effort at Barthez. Elber's aim was true and Barthez had to palm the ball over.

The disappointment for another packed Old Trafford was that Kahn had not been called upon to make a save of the same significance. He soon did, diving low to block an effort from the unlikely source of Silvestre. Just prior to that, Paul Scholes had nearly managed to get to a clever centre from Cole, but if the impression given is of sustained United dominance, it is incorrect.

The game was elongated and its rhythm ding-dong. For every United prod the Germans had one back - literally so in the case of Beckham and Effenberg - and Barthez was soon flying through the air to tip away a screaming 30-yarder from Jens Jeremies. Next a wild Beckham free-kick from the promising position of Bayern's "D"; next a much better offering at the other end from Jeremies. Barthez did well to stand tall.

But, with United drained of imagination, Barthez was most certainly beaten when Zickler smashed a volley against the bar in the 83rd minute. The warning went unheeded. Three minutes later an Effenberg free-kick was met by the head of Thomas Linke, and when the ball bounced Paulo Sergio had skipped free of a static home defence. He poked the ball past Barthez from six yards.

As the banner in the away fans' end predicted, revenge was Bayern's. Now it's United's turn.

MAN UTD: Barthez, Gary Neville, Brown, Stam, Silvestre, Beckham (Yorke 86), Keane, Scholes, Giggs, Cole, Solskjaer. Subs not used: Van Der Gouw, Irwin, Butt, Sheringham, Phil Neville, Chadwick. Booked: Beckham.

BAYERN MUNICH: Kahn, Kuffour, Andersson, Linke, Salihamidzic, Effenberg, Jeremies, Lizarazu, Scholl (Sergio 77), Jancker (Zickler 69), Elber. Subs not used: Dreher, Sagnol, Weisinger, Tarnat, Santa Cruz. Booked: Salihamidzic, Effenberg, Lizarazu. Goals: Sergio 86.

Referee: A J L Nieto (Malaga).