Cristian Rodriguez notched an early opener to shake the home side, before Wayne Rooney brought the score level on 15 minutes.

Late in the second half, Carlos Tevez netted United's second, but when the defending champions looked close to registering a hard-fought win, Mariano Gonzalez canceled out their slender lead.

The visitors came on with all guns blazing, looking for an early goal to take a stranglehold on the game.

Brazilian frontman Hulk, who was at his best, tried his luck on three minutes from close range, but Edwin van der Sar brilliantly parried his shot.

On four minutes, the Portuguese side were fired ahead when Rodriguez cut into the penalty area and opened the scoring with a low shot.

United's sloppy defending encouraged Porto to double their lead, and they tightened their grip on the game for quite some time.

On seven minutes, Porto's Lisandro Lopez released a nice shot, which was easily denied by Van der Sar.

The hosts took a little bit of control after ten minutes, and on the quarter-hour mark numbers were evened up.

Rooney was gifted a one-on-one chance by Bruno Alves, who flicked the ball back to goalie Helton while the England striker was in a very close proximity, to steal the ball and slot home.

After Alex Ferguson's men restored parity, Porto kept the upper hand, with Hulk imposing a great deal of threat upfront.

The second period witnessed a tangible improvement in the Red Devils' performance, while Porto kept up their offensiveness.

Korean midfielder Park Ji-Sung cannoned a fierce shot ten minutes from the hour mark, but the in-form Helton saved it with no trouble.

With United puling up pressure, the away side become dangerous on the counter attack.

Lisandro was about to restore Porto's lead on 68 minutes, but his effort from the box was saved by Van der Sar.

Cristiano Ronaldo, who was clearly out of form, tried to put his team in front on 70 minutes, but his tame shot was no threat for Helton.

The match's tempo was notably stepped up in the last 15 minutes, as both outfits were energetically looking for a winner.

Tevez struck from a narrow angle on 85 minutes after latching onto Rooney's cunning back-heeled assist in the box.

But four minutes later, an unmarked Gonzalez snatched a last-gasp equalizer with a point-black effort.

Porto's opener

United's equalizer

Tevez goal

Porto's final goal