Welshman becomes first player to score in 16 Champions League seasons with a stunning effort from 20 yards after a much-changed Red Devils side had fallen behind in the first half
United had gone behind after some poor defensive work and a good finish from striker Oscar Cardozo early in the first half, but Giggs' goal against the run of play brought last year's runners up a much-needed point against the team likely to challenge them for the top spot in the group stage.
Sir Alex Ferguson went into the game with a gamble, making eight changes to the side that ripped through Bolton Wanderers on Saturday evening, with Wayne Rooney deployed as a lone striker up front and Anders Lindegaard making his first start of the season in place of David de Gea.
Ashley Young missed out altogether, while Nani and Anderson had to settle for a place on the bench, with Sunday’s crunch match against Chelsea seemingly the priority for Ferguson.
And the gamble did not seem to be paying off for most of the first half, with Rooney looking forlorn as he was forced to battle with the towering Luisao for long balls.
The midfield trio of Michael Carrick, Darren Fletcher and Ryan Giggs were not offering much in the way of support or mobility to the striker, and Ji-Sung Park failed to get wide enough to trouble the right-back Maxi Perreira.
The first real effort for either team came Benfica’s way in the 20th minute, with Cardozo forcing Lindegaard to make a fairly routine stop.
And four minutes later, United fell behind through a goal that they really should have cut out.
Gaitan found himself in space near the halfway line after a good turn, and his lofted pass with the outside of his boot found the chest of Cardozo, who turned Jonny Evans twice before striking the ball on the bounce and into the far corner past a helpless Lindegaard.
Evans failed to put in a meaningful tackle while he had the chance, and it was all too easy for Cardozo to find his way to goal, though Patrice Evra must share some of the blame for that after failing to track back and offer his team-mate help.
But it wasn’t too long before United were back level, with their Champions League experience shining through in one individual in particular.
Giggs restored the parity with five minutes to go until half-time, with a stunning drive from 20 yards out into the top corner of Artur’s net, after he was sent running by Antonio Valencia.
With that goal, the Welshman has now scored in 16 separate Champions League campaigns, an astonishing record that puts him one ahead of former Real Madrid striker Raul.
The goal took the match to half-time level, somewhat fortuitously for United who had been below par for much of the game, particularly in the midfield where Benfica were dominating.
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However, the Red Devils came out reinvigorated after the break, and Valencia almost put them in front, after his cross-come-shot was palmed across the face of goal by Artur, but with no United player on hand to supply the finish.
Giggs was next on hand to create a chance, turning back the clock and dancing around flailing challenges before his shot was well blocked by Artur.
Lindegaard then produced a fine stop to justify his inclusion in the team as Benfica broke from a corner en masse, with Cardozo moving to apply the finish from the edge of the area, only for the keeper to shovel the ball away with one hand past the post.
Five minutes later, the Dane was called into action again, palming an effort over the bar from Gaitan which was curling into the far corner.
As the game progressed towards the final stages, it seemed both teams were defending too solidly to offer their opponents the chance to steal all three points.
However, with five minutes left, United narrowly avoided that disappointment, as Cardozo missed a real opportunity, picking up on a rebounding ball to poke wide from an angle only eight yards out.
As the final whistle blew, it was perhaps a fair point for each team though Benfica may argue their first half performance merited more.
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