Ever since Manchester City stumbled into the Europa League, the question put to Roberto Mancini has been a variation of whether winning it would somehow jeopardise their chances of the Premier League. This, however, was a night that questioned whether they are capable of winning it at all.
This is a tie that will take some pulling back in Manchester next week and, but for some fine goalkeeping from Joe Hart, it might have been a disastrous rather than a merely bad evening.
Mancini tried to drag as many positives from the night as he could, although perhaps the most significant moment was not the back-heeled goal that separates these sides but the loss of Vincent Kompany with a calf injury.
The Italian would back a side that destroyed Porto 4-0 in the previous round to hack its way through to the quarter-finals. However fiercely Sporting Lisbon performed in front of their own supporters, they are not a club that travels well, not even within Portugal. Their record of never having been knocked out by English opposition is still under threat.
Nevertheless, despite their obvious resources,City are not a club over-endowed with central defenders and Kompany is the best Mancini possesses. The sight of Joleon Lescott gingerly walking through the Jose Alvalade's reception with a suspected groin strain was a blow upon a bruise.
Mancini will keep his squad at their base in Estoril before flying directly to Wales. There will be training and recovery time but, perhaps most importantly, there will be thinking time. His side only really found a rhythm in the second half once the ponderous, ineffectual figure of Edin Dzeko was hauled off for Mario Balotelli. Nigel de Jong struck the crossbar in a move that was ruled offside and Rui Patricio saved well from Sergio Aguero. But it was not nearly enough.
He argued that City had more chances than Sporting Lisbon but most came after Hart had denied Ricky van Wolfswinkel a glaring opportunity of a second and potentially decisive goal.
The one they did score came from a free-kick, delivered by Matias Fernandez, that Hart pushed away towards Sporting's Brazilian defender Xandao whose first shot was blocked by Hart to which he responded with a fierce back-heel that triggered an avalanche of noise across the stadium.
Whether or not they reach the quarter-finals, this was a night when Sporting badly needed to win. It is a decade since their last title and last season they were eclipsed by the Porto of Andre Villas-Boas. Now they had seen Benfica drive into the quarter finals of the Champions League. When the final whistle was greeted by a mass of green-and-white scarves and banners, the Jose Alvalade resembled what Celtic Park would look like were Celtic good at European football.
For Ricardo Sa Pinto, the youth-team coach pressed into service when Sporting's domestic season was in a state of disintegration this was moment to savour. "I knew we had to be perfect to overcome Manchester City and we played a perfect game," the Sporting manager said, although for real perfection, he would have wanted a second. "I have a lot of respect for Roberto Mancini but I don't agree that we were lucky to win. We did nothing here by accident."
Whatever their manager said, City did not play as well in Lisbon as they had in Oporto, where against the Europa League holders, they rolled out a controlled hugely-effective game-plan to leave with a 2-1 win that was more than enough when the second leg came around.
Possession was squandered too easily and with Gaël Clichy pressed into service as a right-back, there was very little width. Sa Pinto was wearing white elbow patches on his club blazer and he directed his players to exploit the gaps looking like a funky geography teacher.
Sporting's best chance before the interval came in the couple of minutes when City were down to 10 men as Joao Pereira cut between two defenders and saw his shot turned away by Hart. It was his first but not his last save. For Pereira's shot and a cheeky effort from Stijn Schaars as Hart dashed out of his area to head away a clearance, City answered with Kolo Touré's powerful, downward header blocked by Rui Patricio's boot and a curling, beautifully-struck shot from Gareth Barry that missed the post by inches.
In every other aspect of football - particularly in terms of possession and passing - Sporting Lisbon were ahead on points. Six minutes after the restart came the first knockdown blow and it may yet be a knockout.
Man of the match Fernandez.
Match rating 6/10.
Referee C V Carballo (Sp).