Are Manchester Unites still on the ropes?
Lisandro had already seen a viciously swerving shot turned over by Edwin van der Sar when Cristian Rodriguez capitalised on two woeful pieces of United play to open the scoring in the fourth minute.
Cristiano Ronaldo, who had another match to forget, gave the ball away first. Jonny Evans was given a second chance but his clearance was appalling, straight to Rodriguez's feet, and he side-stepped the Northern Ireland defender before curling the ball low to Van der Sar's right.
Confidence flowed through Porto as though sluice gates had been opened and Ferguson's men could easily have been two down before the equaliser arrived.
More clinical opponents would have already dealt United a fatal blow - as it was, Rooney showed that a wounded animal can be the most dangerous.
Bruno Alves, perhaps Porto's most highly-rated player, was guilty of an error of such magnitude that even a schoolboy would have been embarrassed. Rooney's natural instinct made him run to anticipate the back-pass and he gleefully knocked it over the stranded Helton.
Anyone would have expected such a gift to deflate the Portuguese side. Instead it was United who, bafflingly, continued to look rattled while Porto, inspired by the impressively named Hulk, struck fear into United's defenders.
The biggest cheer of the first half at an unusually subdued Old Trafford came when Sunday's hero Macheda warmed up on the touchline.
Anyone expecting a half-time hairdryer to swing the match United's way was destined to be disappointed as Porto continued to break at speed and Van der Sar made another very good save to keep out Lisandro again.
Hulk had a convincing penalty claim against Carlos Tevez before the substitute struck with five minutes to go, after a clever flick by Rooney, to apparently hand United an undeserved victory.
But Porto's good work was not in vain as in injury-time Lucho's cross from the right found substitute Mariano in acres of space at the far post and he took his time before stabbing home.
It will be a daunting second leg for United now, and Ferguson will know that down the East Lancs Road, Rafael Benitez would have been smiling.
