How Roberto Mancini must adore Sergio Aguero the 23-year-old not only scoring the 94th-minute winner that reignited City's hopes of qualifying from what is a difficult Champions League group but also sparing the Italian yet more questions about Carlos Tevez.
No wonder the City manager celebrated as wildly as he did, punching the air like a boxer in a gym, before hugging his coaching staff.
To the rescue: Sergio Aguero (left) celebrates after scoring the crucial winner for Manchester City
MATCH FACTSMan City: Hart, Zabaleta, Kompany, Lescott, Kolarov, De Jong (Aguero 62), Toure Yaya, Johnson (Barry 40), Silva, Nasri (Milner 81), Dzeko
Subs Not Used: Pantilimon, Richards, Savic, Clichy
Goals: Marchena 43 og, Aguero 90
Villarreal: Diego Lopez, Zapata, Marchena, Rodriguez, Catala, Valero, Bruno, Perez (Wakaso 80), De Guzman (Gullon 88), Cani (Mario 82), Rossi
Subs Not Used: Cesar, Musacchio, Bordas, Joselu
Booked: Catala, Rossi, Mario
Goal: Cani 4
Ref: Pavel Kralovec (Czech Republic)
Until Aguero struck late in a mannersynonymous in Europe with that other Manchester club, Mancini must havebeen bracing himself for an uncomfortable few days and not just becausehis team would be staring at two points from their first three encounters in this competition.
A draw against a team sitting 13th inSpain's La Liga would have been seen as a worrying setback ahead of Sunday's Manchester derby and invited further examination of whether Mancini was right to call time on Tevez's association with his side in Munich.
They certainly could have used Tevez last night, the absence of a striker to partner the isolated Edin Dzeko proving a real problem until Aguero joined this contest in the 62nd minute.
Citing Aguero's recent injury problems as a reason why he did not consider him capable of playing a whole game, Mancini left his ?38million signing on the bench and Dzeko on his own because of the suspension being served by Mario Balotelli andthe banishment of Tevez.
Stunning start: Cani (right) puts Villarreal in front against Manchester City
But it made for a difficult match forCity, even if their cause was not helped by uncharacteristically poor contributions from David Silva and Dzeko and the fact that Nigel de Jongstills appears short of fitness.
As masterful as they have been in theBarclays Premier League so far this season, City continue to perform like the novices they are on this European stage.
They might have emerged with three precious points but this was another lesson in the relative complexity of Champions League football; a further insight into the unique challenge this competition represents and one that Mancini and his side have not yet grasped.
Give us a hug! Cani (left) celebrates putting his side in front inside five minutes in Manchester
Again they were caught by a sucker punch, another team skilled in the art of counter-attacking football seizing on an early mistake from Silva and immediately putting City under pressure with a goal from Cani. What you might call a torpedo fromLa Liga's Yellow Submarine.
In fairness to City, their response was spirited. They equalised with an own goal shortly before the break and the arrival of Aguero paid off in the end.
Leveller: Carlos Marchena (centre) put the ball into his own net as City grabbed an equaliser close to half time
But if one of the keys to success on the continent is playing two styles with two teams, City have done precisely the opposite to what they should have done.
They were cavalierin Bavaria with two strikers and cautious here, when Sir Alex Ferguson has long stressed the importance of playing the more offensive football at home.
Back in the game: City celebrate their equaliser against Villarreal at the Etihad Stadium
With Dzeko isolated, Mancini had to make changes. First he replaced Adam Johnson with Gareth Barry in an attempt to provide his principal striker with more support through Yaya Toure; and then he replaced a sluggish De Jong with Aguero. Later on he would also send on James Milner, which again proved important given the pass the Englishman produced to create the decisive goal.
Silva struggled to produce anything close to that kind of quality, and when a fourth-minute pass was delivered short to De Jong it was Jonathan de Guzman who made the interception and Villarreal who were suddenly in control.
Far from happy: Adam Johnson (right) was replaced in the first half after City fell behind to Cani's early goal
First came the shot from Giuseppe Rossi, forcing a save from Joe Hart, and then the close-range finish from Cani, who seized on Hart's failure to parry the initial effort to safety.
With no travelling supporters the only Spanish here were locals the Etihad Stadium fell strangely silent.
But it was not long before Mancini'smen provoked a bit more noise, Aleksandar Kolarov threatening with a long-range effort and Samir Nasri also going close.
Frustrated figure: David Silva looks dejected as City struggled to break down the Villarreal defence
Other opportunities followed for City, and as the interval approached they did play with a bit more composure and cohesion. Mancini's decision to replace Johnson with Barryin the 40th minute helped even if Johnson seemed less than impressed, shaking his head as he passed his manager.
An equaliser within three minutes more than justified the switch, even if it was an own goal from Carlos Marchena that came as the centre half tried to cut out a cross from Kolarov that was intended for Dzeko.
In need of answers: City boss Roberto Mancini watched his side struggle against Villarreal
But all that promise towards the end of the first half disappeared after the break, with City nothing like asconvincing as they have been in the Premier League since that crushing defeat in Bavaria.
Again there were opportunities, and on another day Dzeko might have scored two or three. He was denied by Diego Lopez, the excellent Villarreal goalkeeper, but also by some poor finishing, one close-range header drifting alarmingly wide.
Last-gasp: Aguero (third right) saved Mancini's blushes with his injury-time goal
Mancini was growing increasingly animated, at one stage clashing with the fourth official when it seemed he was trying to take a throw-in.
But when a super pass from Milner sent the excellent Pablo Zabaleta clear, one Argentinian found another with the perfect ball across the face of the Villarreal goal and Aguero struck from close range.
Cue pandemonium, Mancini beating his chest as hard as someone from the visiting camp kicked the away dressing-room door.
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