Some ease into a new job, take their time to acclimatise to fresh surroundings, unfamiliar colleagues and a different style of play. Some do, but Sergio Aguero is evidently not among them. A superstar's scintillating introduction to Manchester City and the Premier League was an exercise in electrifying, an appetite-whetting display of class that was devastatingly cruel to Swansea City.
Caveats can be applied. The division's newcomers were tiring and trailing, relegation favourites whose defenders were all employed in the Championship last season. Reputations are decided in rather bigger matches. Yet this was a debut to rank among the very best, one with such brio it hinted at brilliance. A shot after a minute, a goal after nine, an assist within a further 180 seconds and, to complete his tour de force, a thunderbolt of a long-range strike to bring a brace. Sergio surged into the headlines and the hearts of his new followers.
The hired Kun, the £38 million sharpshooter, turned the climax of an admirable rise up the leagues into a rout. His half-hour cameo exposed the difference between super-rich and working poor. Swansea began with a man who came to the club on trial; their Mancunian counterparts kept their latest Galactico in reserve.
Then, with Swansea's admirable resistance ending, he arrived. His account was opened when Micah Richards drilled in a low cross and a sliding Aguero touched it over the line. Before, juggling the ball over the overworked by still excellent Michael Vorm and hooking it back towards the penalty spot, he set up David Silva for his side's third. Then followed the vicious conclusion to his vignette. "He's not bad," said a deadpan Joe Hart. The more ominous words came from Roberto Mancini. "He needs another two or three weeks to be 100%," said the manager, citing Aguero's late start to training after the Copa America. "He is a fantastic striker."
Brendan Rodgers concurred. "He's a world-class player, his strength and power was superb," the Swansea manager said. "It's a funny one, you come off after the game after losing 4-0 but I said to the players: 'Congratulations, I thought you put on a fantastic show tonight'."
He was right, too, despite the scoreline. While the home fans, as is their wont, chanted "we're not really here", the sentiments could have come from the visitors; nearly non-league in 2003, Premier League in 2011, they accredited themselves well in a first top-flight game for 28 years.
Representatives of a city and a nation, as a proud principality announced its belated arrival in the Premier League, three Welsh flags hung from the top tier of the Etihad Stadium's South Stand. Yet the sight of the dragons was deceptive. The influences were less Cardiff, Caerphilly and Carmarthen than Catalonia. No wonder Manchester City were taken aback.
After 20 minutes, the realisation that the Swansea dressing room doubles up as the West Walian branch of the Xavi fan club set in. Then haves set about demoralising have nots. For a while, though, it was the coulds and the could nots, Swansea starting surreally well with a lesson in possession. Rather than multi-million pound signings, the dominant figures were Kemy Agustien, the former trialist, the diminutive Leon Britton, who played in the game that could have culminated in their relegation from the Football League, and the rhyming right-back Angel Rangel, purveyors of a slick, stylish brand of football. Theirs is less an approach than an ethos.
The same cannot be said of their illustrious opponents, but captivating individuals can transform a team's image. Silva is one such and, at this embryonic stage, Aguero appears another. The jewels from La Liga saw off the Barcelona wannabes.
In this particular tale of two Cities, the difference was both financial and physical. The Mancunian variant have force, and Yaya Toure in particular wrested control of the game back after Swansea's initial excellence, but they also have pace. The underdogs may do in attack, but they possess rather less at the back. Adam Johnson showed as much, leaving scorch marks on the turf to wrench open the floodgates. His shot was parried by Vorm into the path of Edin Dzeko, who seemed to stumble as he prodded it over the line.
That was the breakthrough, and the cue for Aguero. And what ensued may be of more concern to Manchester City's title rivals than Swansea City's defeated defenders.
MAN OF THE MATCH: Sergio Aguero - A fantastic start from a man who only cost twice as much as Jo. There are times when Argentine strikes have been the bane of Mancini's life, but the absent Tevez suddenly seems anything but indispensable. Aguero made his bow playing behind Dzeko; it will be instructive if that is the role he occupies at Bolton on Sunday. One certainty, though, is that he will start.
MANCHESTER CITY VERDICT: Timid at the start, terrific at the end, they could have scored more goals. Both Silva and Gareth Barry hit the bar in the first half and there are signs that they may be able to ditch the tag of a defensive team. With Mario Balotelli an unused substitute and Johnson an unexpected selection, the winger impressed, and he adds the natural width that too few others provide.
SWANSEA VERDICT: Despite the result, plenty emerge in credit, not least the busy goalkeeper, and on this evidence, they look the best equipped of the promoted trio to stay up for a second season. One question to answer is if their neat, intricate football will result in enough chances being created. Hart was rarely involved, even though Swansea had much of the ball, and the other debutant striker, Danny Graham, was the quietest of the visitors.