Rangers 1 - 1 Sporting
Sporting claimed a late away goal to dent Rangers' chances of reaching the last 16 of the Europa League.
Kyle Lafferty and Steven Whittaker threatened for Rangers in the first half while Yannick Djalo had Sporting's best chance before the break.
Whittaker's header on 66 minutes gave Rangers the edge and it looked as though they would take the lead to Portugal for the second leg.
But Matias Fernandez nodded home to turn the tie in Sporting's favour.
Rangers now need to score in next Thursday's return leg to stand any chance of progressing as a 0-0 draw at the Estadio Jose Alvalade will be enough to send Sporting through.
Sporting controlled the midfield area in the first half, with the absence of the injured Lee McCulloch from the Rangers central area leaving the home side without an obvious ball winner.
Sporting could have gone ahead when Postiga collected Evaldo Fabiano's cutback and turned well to angle a shot across the face of goal.
Rangers were struggling to get a foothold in the play and Lafferty was cutting an isolated figure in attack.
But, out of the blue, the hosts carved out an excellent opening as El Hadji Diouf released Steven Whittaker on the right and the full-back's cross was flicked narrowly wide by the head of Lafferty.
Sloppiness crept into Rangers' play and only a last-ditch tackle by captain David Weir spared Steven Davis's blushes after the Northern Ireland midfielder had conceded possession in a dangerous area.
Davis was then required to block Anderson Polga's shot after Bougherra's tame clearance from Pedro Mendes's corner had presented the defender with a shooting opportunity.
Whittaker, a scorer the last time these two sides met in 2008, was unsuccessful with a delicate lob when the ball broke to him in the box off a headed clearance.
Both keepers made vital saves in quick succession with McGregor blocking well at the feet of Yannick after the midfielder had burst into the box and then Rui Patricio diving to his left to keep out Whittaker's powerful shot.
The first half ended with Lafferty heading off target again, this time from a teasing Weiss centre, moments before Diouf was booked for simulation.
Whittaker, deployed in a more advanced role than normal, continued to pose Rangers' most potent threat at the start of the second half and almost scored when he ran on to Lafferty's head-flick and powered in a left-foot shot that Patricio did well to divert wide.
The home crowd were fired up by Rangers' positive start to the second period and it was evident in the Ibrox side's play as Ricky Foster crossed for Lafferty to send a deflected shot wide.
Yannick became the second player to be booked for simulation after he went down in midfield before Sasa Papac's shot whizzed wide of the Sporting goal.
A lung-bursting run by Weiss was brought to an abrupt end when the winger was pulled back by Daniel Carrico, who was perhaps fortunate to escape with only a booking given that Weiss was working his way into a scoring position. Whittaker's initial effort from the free-kick hit the wall and his rebound flew over.
But Rangers got the reward for their positive second-half approach when Weiss's inswinging corner was bulleted home by the head of Whittaker.
Mendes almost scored against his former club when the ball broke to him at the edge of the box, the midfielder's effort spilled by McGregor before the offside Postiga hammered the rebound into the side netting.
Lafferty joined Weiss in being cautioned for dissent and Rangers invited pressure onto themselves by sitting off the play in the closing stages.
And Sporting got the away goal they were searching for when Joao Pereira crossed for substitute Fernandez to head powerfully past McGregor.
Lafferty had more chances in the closing stages as Rangers sought to regain the lead but Patricio was equal to the forward's three efforts at goal to keep the score level.
