A late goal from Ross McCormack earned Rangers a draw against the odds in Porto to keep their Champions League dream alive.
The youngster grabbed the leveller with just seven minutes to go to cancel out Lisandro's header and hand the Scottish champions a precious point.
The result could also help under-pressure Rangers manager Alex McLeish to hold onto his job.
Rangers enjoyed the best possible start to their Champions League campaign when they earned a battling 3-2 win over Porto at Ibrox in the opening game of the competition.
And they knew another decent result against the Portuguese giants at the Stadio Dragao tonight would be a massive boost as they attempt to become the first Scottish club to reach the knockout stages.
A great achievement, maybe, but this game had been overshadowed by the fate of McLeish, after the Rangers boss was told by chairman David Murray his position would be reviewed in early December.
Rangers already had a 3-0 defeat to Celtic under their belts since then, leaving them trailing their bitter rivals by 15 points in the Bank of Scotland Premier League, meaning there was even more at stake against Porto.
Porto coach Co Adriaanse is also a man who knows what pressure feels like after a poor start to their Champions League campaign meant they headed into tonight's game propping up Group H.
The Dutchman added extra spice to the game by claiming he was offered McLeish's job earlier in the year - claims furiously denied by Rangers - but the build-up to the game was more gripping than most of the action on the pitch in the first half.
McLeish admitted he would be unlikely to opt for all-out attack but Rangers struggled to breach the halfway line throughout most of the opening 45 minutes, much less manage any chances on goal.
Porto dominated the opening spell and had the best of the chances early on.
Quaresma weaved his way towards goal, skipping past Alex Rae, before unleashing an angled shot from the edge of the box but the effort was held by Ronald Waterreus.
The Rangers goalkeeper was called into action again when Bosingwa set up Lucho for the volley a couple of yards out but Waterreus managed to block.
The home side were threatening again when Bosingwa whipped another dangerous cross into the box only for Lisandro to send his header just over the crossbar.
Quaresma was looking dangerous on the left wing and he was causing problems for Rangers again when he squeezed between two defenders before trying his luck with the shot but the effort hit the side-netting instead.
The home side picked up where they left off after the break - putting the Rangers goal under pressure.
Within three minutes of the restart, Lucho tried his luck with an opportunistic 25-yard drive but the shot was comfortably smothered by the Rangers goalkeeper.
It was only a matter of time before Porto broke the deadlock and the breakthrough came after 60 minutes.
Bosingwa delivered the cross to the back post and both Lisandro and Sotirios Kyrgiakos jumped for the ball but it was the Porto player who connected with the header to nod past the helpless Waterreus from six yards.
Rangers immediately made a change, swapping Rae for forward Steven Thompson, in the hope of hauling themselves back into the game.
With little in the way of creativity up front, Rangers needed to make the most of their set-pieces but Kyrgiakos failed to connect with McCormack's free-kick at the back post and the chance was lost.
Just when it looked like Rangers had no chance of salvaging anything from the game, they stunned their hosts by pulling a goal back with seven minutes to go.
Chris Burke did well to cut the ball back into the path of his fellow substitute McCormack to bullet home from 10 yards and hand Rangers a crucial point.
