MANCHESTER - FC PORTO scored a pair of valuable away goals on Tuesday to earn a 2-2 draw at defending champion Manchester United in the first leg of the Champions League quarterfinals.

Arsenal had to come from behind to draw their game 1-1 against Villareal in Spain.

But first, over at Old Trafford, Porto substitute Mariano Gonzalez scored the equalising goal in the 89th minute, four minutes after Carlos Tevez had made it 2-1.

United trailed for the first time in its title defense in the fourth minute when Jonny Evans' poor clearance allowed Cristian Rodriguez to put Porto ahead.

But the visitors also had some sloppy defending, and Wayne Rooney took advantage of it to equalise in the 15th by pouncing on a lax backpass from Bruno Alves.

Manager Sir Alex Ferguson slammed his side's lack of concentration as Porto hit back late on to take a draw.

"(The result) was about right - first half they were the better side but second half we improved and got more possession," the Scot told ITV1.

"But getting the (second) goal the way they did - we should really have defended that. It was a bad goal to lose," he added.

Meanwhile in Spain, Emmanuel Adebayor's superb overhead strike secured Arsenal a 1-1 draw away to Villarreal.

The game was only 10 minutes old when Villarreal midfielder Marcos Senna received the ball outside the area and scored with a fierce drive that flew into the top corner.

Arsenal were hindered by first-half injuries to goalkeeper Manuel Almunia and defender William Gallas who both had to be substituted, as Villarreal dominated.

But the Londoners responded in the second half and Adebayor's acrobatic strike from Cesc Fabregas's pass in the 66th minute left the visitors with an away-goal advantage.

The return leg for both Manchester United and Arsenal will be played on April 15. -- AP, REUTERS