Sergio Aguero has been Manchester City’s most reliable goalscorer for so long that it had become almost impossible to imagine life without him.
The club’s greatest ever striker was at the forefront of City’s decade of success, from the unforgettable injury-time winner against QPR that clinched the 2012 Premier League title in the most dramatic of circumstances, all the way through to his strike in last season’s Carabao Cup final.
After 256 goals from 379 matches over nine-and-a-half years, Aguero’s place in City's history books has long since been secured.
However, Pep Guardiola's side have got used to playing without their talisman, mainly through necessity.
Aguero has always been vulnerable to muscular problems but the last six months have been difficult for the Argentine, who suffered a knee injury in City's second game after football returned from its coronavirus-enforced suspension of play last year.
He underwent surgery last June but did not feature again in the 2019-20 campaign. His recovery spilled over into this season, while he has also been hindered by a hamstring issue. The net result is that Aguero has managed just 260 minutes of game time to date.
Guardiola planned to start Aguero in Sunday's FA Cup third-round clash with Birmingham but the unlucky 32-year-old was forced into self-isolation after coming into contact with a person who tested positive for Covid-19, meaning he can't play against Brighton on Wednesday night either.
Aguero’s absence during the opening months of the season was a major issue for City, with the Premier League's top scorers in each of the past three seasons netting just 10 goals in their opening eight matches.
However, over the past month, City have found their shooting boots, scoring at least two goals in each of their five last matches.
Guardiola has always refused to blame his strikers when his side have gone through dry spells, arguing that goals should come from every position. Well, having shored up his defence, providing the foundation for a 13-game unbeaten run, the Catalan has now seen City rack up six straight victories featuring 10 different scorers.
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Suddenly, the goals from everywhere, and every scenario.
In the Carabao Cup semi-final victory over Manchester United, City took advantage of their rivals' set-piece frailties, with defender John Stones scoring from a free-kick and deep-lying midfielder Fernandinho volleying home a poorly-cleared corner.
Meanwhile, the recent victories over Birmingham, Newcastle, Arsenal and the standout performance away to Chelsea were characterised by the kind of dynamic and incisive attacking play for which City are renowned.
Guardiola has played with five attacking players and a fluidity that has made it difficult for opponents to stop them.
At Stamford Bridge, for example, Kevin De Bruyne started as the false nine, with midfielders often running beyond him into the area, and the opening goal came courtesy of central midfielder Ilkay Gundogan, who was the furthest player forward and in a central position.
Against Birmingham at the weekend, striker Gabriel Jesus was recalled after missing three matches following a positive Covid-19 test, but he spent much of the game on the left flank, with winger Riyad Mahrez often playing through the middle.
But it is not a rigid formation. The opening goal came when Mahrez drifted back out to the wing to open up space for Bernardo Silva to drift through the middle. And the third goal underlined the flexibility of the system, with De Bruyne on the left wing and Silva on the right when Phil Foden burst through the centre to score.
With everything clicking once again, both in defence and in attack, there is an undeniable feeling that City are on the march. Certainly, with Brighton at home representing the first of three winnable Premier League games in the space of 10 days, Guardiola is a happy man right now.
Aguero, though, will be concerned. With so many of his team-mates now finding something resembling their best form, it will be difficult for him to force his way back into the side when he is available again. Indeed, the Argentina international often needs plenty of game time to get back up to full speed.
There is no doubt that Aguero can adapt to City's new style. He may do his best work in the box, but he has developed his game immensely well since Guardiola joined the club, adding hard running and the ability to drop deep to his game.
The striker will also be buoyed by his manager's desire to have him available again as soon as possible.
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"Only I know how much I miss him,” Guardiola said before the Birmingham clash. “Just look at the quality he has in the box: he is unique. Unfortunately, he had a really tough injury and what is important is that his mood is exceptional, better than ever.
"He is an important part of the group, incredibly loved and the feeling is that, in the last 10 days to two weeks, his knee has been good after training and this is the best news we could hope for.”
But will be an immense source of frustration to Aguero that he cannot show right now just how valuable he remains to City's squad. After all, he has just six months left on his current contract.
His camp have suggested that there has been no contact from City over an extension, although the club said at the start of the campaign that his future will be worked out between the two parties, just as it was with Guardiola’s recent two-year extension.
Paris Saint-Germain have been linked with Aguero, who turns 33 in June, and there is no doubt that City are already considering signing a successor, whether it’s this summer or next.
City continue to be linked with Barcelona captain Lionel Messi, who will also be a free agent at the end of the season, while Borussia Dortmund's Erling Haaland is another potential target.
Aguero, for his part, is understood to be happy in Manchester and determined to make an impact in the second half of the season – not least in the Champions League, which remains the only major trophy to have eluded him at club level in Europe.
Guardiola enthused, “He is so optimistic, saying he will have a good season and score lots of goals."
Aguero's first goal, though, should just be getting back into City's starting line-up.