Then Sterling took centre stage after the break, claiming a stunning treble inside 11 minutes to go alongside his earlier assist as well as winning a penalty to cap another superb individual display.
The only downsides on the night were a red card for Phil Foden, who was dismissed seven minutes from time after picking up two yellow cards and a knock to Rodri who had to be substituted just before the break.
Backed by a noisy travelling contingent of fans, Atalanta demonstrated why they are Serie A’s top scorers in the early stages, committing men forward and displayed no sign of nerves.
The visitors almost opened up the City defence inside five minutes through Josep Ilicic and there was another huge scare on 11 minutes when Malinovskyi’s slide rule pass found Robin Gosen clear on the left flank.
His cross was straight and true but fortunately Timothy Castange’s radar was not – his header sailing over the bar.
Foden, making his second start of the season, almost provided the perfect riposte as he jinked through the Italians’ defence before being sent tumbling to the ground by Berat Djimsiti.
Referee Orel Grinfeld waved away home appeals for a penalty but it did serve to fire City up.
Foden and Sterling then linked superbly to befuddle the visitors’ defence only for Sterling’s cross to just evade the waiting Aguero who subsequently blazed over from 10 yards after more dazzling work by Foden.
Atalanta though were not deterred, and their persistence saw them take the lead via a 27th minute penalty.
The ever-dangerous IIcic launched a lightning right wing raid and Fernandinho mistimed the tackle, bringing the striker down just inside the box.
Ruslan Malinovsky coolly converted the spot-kick to leave City with work to do.
The response was decisive and almost immediate.
As so often, Sterling was the architect, the England winger drifting in from the left before delivering an exquisitely timed cross which the waiting Aguero – making his 100th appearance in European club competitions, gratefully gobbled up to restore parity.
Three minutes, the Blues had completely turned the game on its head as we took the lead.
The England man drifted inside the Atalanta defence a merry dance before being felled in the box by Andrea Masiello.
Master predator Aguero needed no second invitation as he rifled home the penalty to double his and City’s tally.
There was an injury worry for City just before the break with Rodri having to be replaced by John Stones after hurting his leg before Walker then warmed Atalanta keeper Pierluigi Gollini’s hands with a rasping deflected drive.
The second half then saw Sterling take centre stage as the England international provided further confirmation of his peerless talent
Sterling effectively put the game to bed as he claimed City’s third goal on 57 minutes.
The teenager unselfishly steered the ball into Sterling’s path and Raz blasted home from close range.
Seven minutes from time the one sour note saw Foden be dismissed after he picked up a yellow card for pulling De Roon back.
Who else but Raheem?
A day after being included on the short list for the Ballon d’Or Sterling provided yet more evidence of his wonderful all-round ability.
Not only did he bag an 11 minute hat-trick – his fourth treble of 2019 – he also provided an assist and won City’s penalty.
All in all, not a bad night’s work!
Ton up Aguero
On what was his 100th appearance in UEFA club competition, our all-time record goalscorer again proved the man for the big occasion.
Kun was at his lethal, instinctive best in perfectly timing his run to meet Raheem Sterling’s inviting cross for our leveller.
And the Argentine then again demonstrated his nerves of steel by drilling home a fine penalty to put the Blues into the lead.
As usual, Sergio makes the difficult look easy.
“All the credit is for Raheem. He’s a guy whose physicality is incredible. He is so strong."
“Day after a game, he could play another.
“His regeneration is incredible; he can play both sides. He is an extraordinary player.”
And asked whether he felt Sterling could get even better yet, the boss said he felt the England international possessed the necessary desire.
“It depends on him. His desire, I think he has that. The desire to be better.”
What it means
City remain in top spot at the halfway stage in Group C with nine points from our first three games.
Shakhtar Donetsk and Dinamo Zagreb, who drew 2-2 earlier tonight, are in joint second place with four points apiece.
City return to domestic duty on Saturday lunchtime when we play host to Aston Villa in another crucial Premier League encounter.
Kick off at the Etihad is 12.30pm (BST).