Mariano strike stuns United

After trailing to Cristian Rodriguez's fourth-minute opener, United had profited from a large slice of luck when Wayne Rooney netted the equaliser.

And when Rooney set up Carlos Tevez to put the Red Devils in front five minutes from time it seemed Sir Alex Ferguson's men would take the narrowest of leads to Portugal next week, only for an unmarked Mariano to deny them at the death.

Even before they scored, Porto had served notice that their speed and slick passing game was going to be difficult to contain. Lisandro Lopez drew an excellent save out of Edwin van der Sar after leaving Jonny Evans looking distinctly flat-footed.

And after one escape, Porto were in no mood to offer another as a slack pass from Cristiano Ronaldo put United under pressure, just as it did on Sunday.

Lisandro swung over a cross that Evans should have dealt with comfortably. Instead, he prodded the ball straight to Rodriguez, who took a stride forward before calmly curling a shot into the bottom corner.

There was certainly no need for an inquest as to how the home side got their equaliser. Alves turned Aly Cissokho's square pass back to Da Silva Helton, but had not bothered to look and spot Rooney in a position that required only the finish, which the England striker delivered with nerveless authority.

For all United had gained a solid foothold in the contest, Porto were still an electrifying attacking force throughout the second half.

But when substitute Tevez turned home Rooney's sublime back-flick five minutes from time, it seemed as though United had ridden out the storm.

But, as the celebrations rang round the stadium, Porto powered up to the other end where Mariano did his own supersub impression, drifting into space at the far post to finish off Lisandro's cross.