Porto Snatch a Draw
Manchester United were distinctly off-colour, whilst Ronaldo was completely marked out of the game by his Portuguese compatriots, who obviously recognised his attacking threat.
United looked like they had got away with it, scoring a goal with five minutes to go to put them into the lead, but Porto equalised in injury time with what could be a priceless away-goal.
If Federico Macheda's late winner against Aston Villa on Sunday was supposed to have rejuvenated United after Premier League defeats against Liverpool and Fulham, there was little evidence of their recovery at a subdued Old Trafford.
United gave away possession at will and displayed the sort of alarming defensive vulnerability that was first exposed in the home defeat against Liverpool.Throw in a disjointed midfield and an attacking effort that relied almost solely on the inspirational Rooney, and all the ingredients were in place for the visitors to produce a shock.
Slack at the back, careless in possession and lacking any spark of invention, their only comfort was that they reached the interval on level terms after being outplayed and outsmarted by Porto. Porto posted the first warning inside two minutes when Lisandro Lopez's powerful shot was turned over the top by keeper Edwin van der Sar with United's defence exposed.
It was the shortest of reprieves and a sign of things to come as Porto were rewarded with an away goal after only four minutes that summed up everything about the difference between the two sides in the opening exchanges. Cristiano Ronaldo conceded possession wastefully before a lapse of concentration from Jonny Evans allowed Rodriguez to cut in and curl a precise finish beyond Van der Sar to leave Old Trafford stunned into silence.
United's response was a Ronaldo header that was clawed away by keeper Helton - and they were allowed to draw level after 15 minutes courtesy of a monumental defensive miscalculation from Porto defender Alves. Porto were in no danger as the defender decided to try and find keeper Helton with a back-pass, blissfully unaware that Rooney had anticipated the move. The interception was as inevitable as the finish, coolly lifted over Helton by the England striker once the keeper had committed himself.
This should have been the cue for United to resume normal service and emerge from their shaky start. The opposite was true and Porto were presented with a host of chances to regain the lead. Rodriquez shot straight at Van der Sar when well placed and Lopez was inches away from connecting with Lucho's pass at the far post with no United defender in the vicinity.
And Old Trafford vented its fury on John O'Shea when more hapless defending gave the appropriately named Hulk an opportunity which, fortunately for United, he wasted. United improved as half-time approached and Paul Scholes almost gave them a half-time lead when he headed over from Patrice Evra's cross.
Ferguson's brisk march down the touchline as the half-time whistle sounded hinted at the dressing down United were surely going to receive - and they resumed with a predictable increase in energy levels after the break. Eccentric keeper Helton kept United at bay as they finally exerted a measure of supremacy, turning Rooney's clever chip over the top and diving spectacularly to save Vidic's header from substitute Ryan Giggs's corner.
Porto were still a danger on the break, and twice Van der Sar was called into action to save from Lopez and Raul Meireles as United received a reminder of the threat the visitors still posed.
Ferguson sent on Tevez, as demanded by the Old Trafford crowd, and he was rewarded when he profited from Rooney's superb flick to power a finish past Helton at the near post. But as United looked to have staged yet another dramatic late show, there was one last twist when Lucho set up Mariano, who was left unmarked to bear Van der Sar at the far post.
United's players departed with only the cheers of Porto's fans to accompany them - and with an uphill task in Portugal next week to stay in the tournament.
Man Utd: Van der Sar, O'Shea, Vidic, Evans (Neville 72), Evra, Fletcher, Carrick, Scholes (Tevez 72), Ronaldo, Rooney, Park (Giggs 58).
Subs Not Used: Foster, Eckersley, Nani, Macheda.
Goals: Rooney 15, Tevez 85.
FC Porto: Helton, Sapunaru, Rolando, Bruno Alves, Cissokho, Lucho Gonzalez, Fernando, Raul Meireles (Costa 79), Lopez, Hulk, Rodriguez (Mariano Gonzalez 79), Costa (Madrid 90).
Subs Not Used: Nuno, Stepanov, Farias, Sektioui.
Booked: Bruno Alves, Helton.
Goals: Rodriguez 4, Mariano Gonzalez 89.
Ref: Konrad Plautz (Austria).