Manchester - Mariano Gonzalez scored a late equaliser as Porto held Manchester United to a 2-2 draw in the first leg of their Champions League quarter-final at Old Trafford on Tuesday.

The visitors took a fourth-minute lead through Cristian Rodriguez, only for a defensive howler to present Wayne Rooney with an equaliser 11 minutes later.

Substitute Carlos Tevez looked to have given United the win when he struck with five minutes remaining, but Mariano ghosted in at the back post to steal an equaliser three minutes later.

For United the worry is that, since being eliminated from the competition by Porto in 2004, they have never lost a European tie in which they had the second leg at home, and have never won one in which they have played the second leg away.

The Portuguese champions had gone unbeaten in 22 Champions League and domestic league matches before last night, and their attacking approach unsettled United.

Hulk had already drawn a fine save from Van der Sar when Porto went ahead.

Cristiano Ronaldo gave away possession, and when Jonny Evans made a hash of clearing Cristian Sapunaru, Rodriguez pounced, creating space before curving a precise finish into the bottom corner.

United looked shaky at that stage but, after Helton had made a plunging save form a Ronaldo header, Porto gifted United the equaliser.

Bruno Alves was under no pressure when, without looking, he rolled a backpass straight to Rooney, who took the chance with casual ease.

That settled United to an extent, but they still looked shakier at the back than they did in the early part of the season.

Raul Meireles headed a Lucho cross straight at Van der Sar, while Hulk's directness was a constant threat.

Slowly, as the second half wore on, United began to assert themselves, but the game remained remarkably open.

Rooney drew a back-pedalling tip-over from Helton with an opportunistic chip just before the hour and, from the resulting corner, the Brazilian goalkeeper was called into another block to keep out Nemanja Vidic's header.

Van der Sar was then called into saves from a deflected Lisandro shot and a long-range Aly Cissokho effort.

With five minutes remaining, Rooney flicked on a Gary Neville throw-in for Tevez to lash into the roof of the net.

But the celebrations had scarcely subsided when Lisandro's cross found Mariano at the back post, and he helped the ball over Van der Sar to make it 2-2, and give Porto the advantage in the tie.

The sides meet again in Portugal next Wednesday. (dpa)