Ruben Neves got Portugal out of jail with an injury-time World Cup qualifying winner against the Republic of Ireland after Cristiano Ronaldo had seen his penalty saved by Caoimhín Kelleher.
Heimir Hallgrimsson's men looked set to leave Lisbon's Jose Alvalade Stadium with a hard-fought point but ultimately did so empty-handed, although having restored a good deal of price with a battling display which erased some of the memories of last month's embarrassing defeat in Armenia.
Defeat, however, leaves them staring down the barrel, with their first three Group F games having yielded just a single point.
They must beat the Armenians in Dublin on Tuesday evening, when key midfielder Josh Cullen will be suspended, if they are to have any hope of claiming a play-off place.
Just as they had done in 2021, the Portuguese left it late, Neves heading home in the first minute of stoppage time to snatch a 1-0 win, four years after Ronaldo had scored twice at the death to see off a stubborn Ireland.
Hallgrimsson adopted a safety-first approach after seeing his side concede twice in each of the first two qualifiers, setting up in a 5-4-1 formation designed to frustrate.
Nuno Mendes volleyed a seventh-minute Neves cross powerfully across Kelleher's goal and Bruno Fernandes curled a right-footed shot well wide of the goalkeeper's left post two minutes later to maintain the pressure.
However, the 'keeper needed the help of a post when Ronaldo made enough space for himself to unleash a snapshot which flew past Kelleher and came back off the woodwork at such pace that Bernardo Silva could not steer the rebound into the empty net.
Applause rang around the stadium in memory of Diogo Jota as the game entered its 21st minute, just as Ireland started to ease themselves up the pitch, with Festy Ebosele's power taking him past Mendes to deliver another cross and Jayson Molumby clearing the crossbar with a strike from distance.
Kelleher was sent back-pedalling by Vitinha's 38th-minute shot after it looped up off defender Jake O'Brien and then had to claw away Goncalo Inacio's flick from a Fernandes corner before fielding the Manchester United midfielder's speculative drive to preserve his clean sheet on the half-time whistle.
Ronaldo attempted to take matters into his own hands after the restart with two attempts in quick succession but sent both wide, while Vitinha was similarly inaccurate when presented with a half-chance.
Disquiet was mounting within the Portugal camp and Ronaldo pointedly grasped the ball and placed it down for Kelleher before applauding sarcastically in an attempt to encourage him to take a goal-kick more quickly.
The Ireland 'keeper saved well from Neves after he was allowed to run from his own half as the hour mark approached and then repelled Vitinha's attempt after Fernandes had dummied Silva's pull-back.
Ronaldo stabbed wide from substitute Nelson Semedo's 71st-minute cross and his pain increased with 15 minutes remaining when Slovakian referee Ivan Kruzliak awarded a penalty after Francisco Trincao's shot hit Dara O'Shea's arm and Kelleher brilliantly saved his spot-kick with his trailing leg.
But Neves came to his side's rescue when he headed Trincao's cross past Kelleher to win it.
