Ever since Manchester City stumbled into this competition, the question put to Roberto Mancini has been a variation of whether winning it would somehow jeopardise their chances of winning the Premier League. This, however, was a night that questioned whether they are capable of winning it at all.
In order to reach the last eight, this is a tie that will take some pulling back at the Etihad Stadium and it was a game that Manchester City might have lost disastrously.
They were as disjointed here as they had been slickly impressive in the previous round against Porto and the loss of Vincent Kompany through injury was a blow upon a bruise.
Mancini will keep his squad at their base in Estoril before flying directly to Wales for Sunday's encounter with Swansea. The Italian has arranged practice facilities for his team, but the short break will allow the Manchester City manager some thinking space.
For all the talk of whether he might like to sign Robin van Persie -- and frankly Lee van Cleef would have been more effective than Edin Dzeko last night -- it is the men he trains now that matter.
Had Joe Hart not saved brilliantly from Sporting Lisbon's Dutch striker, Ricky van Wolfswinkel, who ought to have finished Emiliano Insua's cross much more decisively, Sporting Lisbon would be taking a two-goal lead with them to Manchester.
The goal they did score was from a free-kick delivered by Matias Fernandez that Hart stretched for and pushed away. Xandao was on hand to meet the rebound, saw it blocked and then drove it into the net with a fierce back-heel.
The Jose Alvalade exploded. Last season they were eclipsed by the Porto of Andre Villas-Boas and they had just seen Benfica drive into the quarter-finals of the Champions League. This was their chance for a bit of glory and it was one they seldom looked like squandering, although when Mancini pushed on Mario Balotelli for Dzeko, a rhythm of sorts was found.
Manchester City's displays around Europe have been bitty -- defeat in Munich and Naples, an efficient display at Villarreal and a superb one in Porto. This, however, was, in many ways, the most worrying of them all and although they will back themselves in Manchester, it may be the last European outing of the season.
With its curved roof and girders decked out in green and yellow, the Jose Alvalade resembles what Carrow Road might look like should Norwich ever redevelop their stadium. It has never had the same aura as Lisbon's Stadium of Light, but it has equally never been particularly kind to English teams.
City's squad may not have been able to name many of Ricardo Sa Pinto's players, but one of Sporting's proudest boasts was they had never been knocked out by English opposition. It was a statistic that was likely to be rigorously tested.
Nevertheless, however well they had performed in eliminating what on paper was a vastly superior Porto side in the previous round, Mancini was right to say this would be serious business and within eight minutes he had lost his captain.
There was nobody around Kompany when he pulled up with what looked like a serious calf injury. City's resources may be enormous, but they are not exactly overburdened with high-quality centre-halves and for however long he is out, City will carry a certain vulnerability.
They did not play as well in Lisbon as they had in Oporto, mainly because with Gael Clichy pressed into service as a right-back, there was 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.
In terms of clear goalscoring opportunities, the half-time score was a draw. In every other aspect of football -- particularly in terms of possession and passing -- though, Sporting Lisbon were ahead on points. (© Independent News Service)