The Scottish champions matched the home side in the first half but after the break the Paraguayan international striker twice hit the woodwork and was denied by a world-class save from Artur Boruc.

But in the 86th minute Cardozo beat the offside trap to knock the ball past Boruc, leaving the Glasgow side 14 group games without a win away from Parkhead in the group stages.

The visitors can have little complaints after a second half which saw them enjoy some good fortune in the Stadium of Light before they eventually succumbed late on.

However, qualification to the knockout stages for the second season in succession now looks unlikely for the Glasgow side.

Gordon Strachan's reshuffled side took many pundits and fans by surprise, particularly the omission of on-form Scott McDonald and the talismanic Shunsuke Nakamura.

The early moments, inside a barely half-full stadium, did little to indicate the Celtic boss had pulled a masterstroke although by the end of the first half, despite a couple of nervy moments, there was a real sense of belief among the visitors.

The home side's first effort on goal came in the 13th minute but midfielder Augustin Binya's effort from distance sped wildly past Boruc's goal, summing up the early malaise in the encounter.

The Portuguese side looked a shadow of the team that beat Celtic 3-0 in the same venue a year previously while Celtic remained strangely tentative.

However, midway through the first half, Aiden McGeady's short back-header to Gary Caldwell, intercepted in the penalty area by Leo, almost led to a Benfica opener.

The Brazilian defender whipped the ball back from the byline but the onrushing Cardozo missed his kick altogether allowing the ball to fly away from the danger zone.

Celtic, however, slowly grew in confidence. In the 33rd minute Paul Hartley's deep cross into the Benfica box reached Killen and his headed knockdown found midfielder Massimo Donati racing in, only for his effort from eight yards out to bounce straight at goalkeeper Quim.

Five minutes from the end of the first half, Celtic midfielder Jiri Jarosik set up Scott Brown at the edge of the Benfica box but his drive went wide of the target but it was another warning for the home side.

But two minutes later, after Killen had bravely blocked a goalbound effort from Cardozo, Boruc brilliantly tipped a Konstantinos Katsouranis header from 12 yards over the bar as Benfica finished the first period with a flourish.

Referee Massimo Busacca, whose kit had clashed with Celtic's dark green away strip in the first half, changed to a luminous yellow top at the interval.

Benfica started the second period brightly and in the 50th minute Boruc had to pull off a great save from a point-blank Cardozo header.

The Lisbon side went down both flanks looking to prise open the Hoops' defence but the Parkhead men held firm and found time to set up the occasional counter-attack.

In the 56th minute Killen latched on to a McGeady cutback at the near post but his effort hit the side-netting.

Moments later, Quim had to throw himself to his left to push McGeady's drive from 16 yards past the near post.

Just past the hour Benfica replaced Nuno Assis and Gonzales Bergessio with Freddy Adu and Angel Di Maria - and soon after Cardozo hit the bar from close range after Boruc had parried a long distance drive from Rodriguez.

Moments later, as Celtic struggled to keep their shape, Cardozo had another effort which rebounded off the post.

Cardozo had another deflected effort in the 73rd minute which sneaked past the far post - and as the traffic continued to make its way towards the visitors' goal Boruc made another good save from the head of the same player, after Hartley's miskick in front of goal had put his team under pressure.

But the tireless Cardozo was not to be denied and in the 86th minute he beat the offside trap to bring down a Di Maria chip and knock the ball past Boruc.