For if you leave a top-six team to join a club who have won one Premier League match in 10 and seemingly heading for the Championship, and for a sum as huge as £24million, then an immediate effect is required.
Quick off the mark: Darren Bent took just 18 minutes to open his Aston Villa account
Inspiring the defeat of billionaire title contenders Manchester City, who had lost one game in 17, pretty much meets the mark.
As City's title ambitions took a heavy blow, from which they may not recover, Villa's season seemed revived. True, they rode their luck and undoubtedly relied upon inspirational performances from Richard Dunne and James Collins. Yet if they can play with the verve and vigour they displayed last night, they will surely remain in the Premier League.
Their match-changing moment was inevitably Bent's moment. It came on 18 minutes and though it was not quite his first touch of the game, it was certainly his first significant contribution.
When Joe Hart failed to deal properly with Ashley Young's splendid shot, pushing the ball back into the danger area, who should be first to react? Who had anticipated the rebound? Who was ever alert to the possibility of some goal scraps? Of course, it was the debut man.
Making his point: Bent became an instant hit with Villa supporters
Cool as you like, he struck his opening goal for Villa confidently past the sprawling Hart, who failed to recover from his initial error. It is for moments like this that even the most equitable Premier League chairmen blow their millions in a blind panic when threatened with relegation.
Bent's instincts and the goal itself transformed the mood at Villa Park. 'One Randy Lerner,' chanted the Villa fans in delight . and that has to be worth £24m of any man's money.
'People have opinions and it's been a hard week,' said Bent. 'But these are the occasions we enjoy and I'm going to enjoy it tonight.' No doubt he did.
'The finishing touch was just like a natural-born goalscorer,' enthused his manager Gerard Houllier who, like Bent, must have felt a degree of anxiety, lest his gamble did not pay off.
Still waiting: £27million man Edin Dzeko (left) is yet to score in England
'It's something you can't teach because he was full of composure. That goal was a reflection of his class. And that's what he's here for: to score goals.'
City manager Roberto Mancini departed early to visit his elderly and ailing father in Italy, leaving assistant Brian Kidd to explain how a title challenge might be rebuilt, given that even before the game they knew that Arsenal and Manchester United were stretching away.
'It is a blip, with Manchester United going so well,' said Kidd.
'Personally, I think it's United's to lose but obviously we're disappointed. But we'll be in tomorrow for training and our aim at the start of the season was to be in the top four.
'Obviously when you're playing at 5.30pm, you know the results beforehand but that didn't influence us. The boss has always said, "We work hard; we look to improve". We lost against Everton (in December) and since then the response has been very good and no doubt they will respond again.'
In reality, the game should have been City's, though there was a perverse delight in watching Mancini's team frustrated in their endless, yet fruitless, possession by a redoubtable back four and tireless midfield.
Indeed, Mancini was watching a mirror image of his own team when they take on better opponents. Villa defended stoutly, none better than Collins, whose block from Carlos Tevez on 79 minutes epitomised his evening.
'Our defending was resilient, brave, courageous - and with a bit of luck at times,' admitted Houllier. 'Both Richard and James blocked and stopped almost every shot they had so we had almost three goal-keepers. The back four were immense.'
No less impressive were Stewart Downing and Ashley Young. They might not be everyone's idea of a central midfield, but they were the model of discipline throughout. Yet City were disappointing in their lack of incisive play, none more so than ex-Villa star Gareth Barry, who endured the derision of his old fans all evening, right up to when he was substituted on 56 minutes.
No love lost: Gareth Barry (centre) was routinely booed on his return to Villa Park
His replacement, Adam Johnson, added penetration but City were frequently forced wide, could not breach the defensive lines and were often reduced to long-range shooting.
Jerome Boateng fired in one on 61 minutes which Brad Friedel did well to parry and there were others from Alex Kolarov and Adam Johnson on 75 and 76 minutes respectively.
A plaintive moment occurred when Edin Dzeko produced a great turn and a delightful cross, yet no City player was prepared to attack the six-yard box to connect.
Perhaps inevitably, a panicky final 10 minutes produced their best chances. De Jong, from a ferocious shot that deflected off Ciaran Clark, struck the post with Friedel stranded. Then a delightfully flighted cross from David Silva landed perfectly on the head of Dzeko on 84 minutes. All the £27m man had to do to ruin Bent's debut was direct the ball goalwards, but he headed wide.
It spoiled an otherwise encouraging performance from the Bosnian. No doubt his time will come; Bent's already has.
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Explore more:People: Carlos Tevez, Edin Dzeko, Darren Bent, Richard Dunne, Joe Hart, Adam Johnson, Ashley Young, David Silva, Stewart Downing, Gareth Barry, Gerard Houllier, Brian Kidd, Roberto Mancini Places: Italy