MILAN -- Manchester City produced a chaotic second-half display in a famous old stadium on Wednesday. They cannot afford another on Sunday.

A trip to the San Siro is usually the highlight of any European campaign, but beforehand, this one was reduced to a glorified warmup with Anfield and Liverpool to come in four days' time. That, though, was before Atalanta jolted City during a cavalier second 45 minutes, Gabriel Jesus missed a VAR-awarded penalty, Ederson was substituted at half-time, Claudio Bravo was sent off and Kyle Walker ended the night in goal.

The bare facts are that the game ended 1-1 and City will have to wait to qualify for the knockout rounds. Pep Guardiola, though, had said the best way to get ready for Liverpool was with a polished display here and, in the second half at least, it was far from it.

The sight of Kevin De Bruyne arrowing the ball out of play with Joao Cancelo in acres of space summed up a second-half performance that lacked the usual swagger and spark.

"In the second half we suffered a lot," Guardiola admitted afterwards.

Despite starting the night with a five-point lead at the top of Champions League Group C, he stuck to his word and picked a strong team. Ederson, Fernandinho, Ilkay Gundogan, Bernardo Silva, Raheem Sterling and De Bruyne were all asked to start against a team who were demolished 5-1 at the Etihad Stadium just two weeks ago.

With Aymeric Laporte, Leroy Sane, Oleksandr Zinchenko and Rodri injured and Phil Foden suspended, Guardiola could argue he had no one else, but there was still an element of risk given the size the game they face next. If Ederson, forced off at half-time, is not available at Anfield, the gamble will not have paid off: Bravo, sent off for bringing down Josip Ilicic nine minutes from time, has not started a league game since May 2018.

Walker, for his part, kept a clean sheet and was serenaded by the visiting fans at the end with chants of "England's No. 1." The right-back has occasionally taken part in goalkeeping sessions at the City Football Academy.

The result should never have been in doubt beyond the seventh minute.

Atalanta midfielder Remo Freuler joked in his pre-match news conference that City are so good they can thread passes "through your earhole," and while Bernardo's wasn't quite that accurate, it still carved open the home defence for Jesus to flick into Sterling's path. Sterling doesn't often miss these days, and the City fans high up behind Ederson's goal were already celebrating before the ball was casually ushered into the corner with a swing of the winger's right boot. That's 18 in 20 games for club and country this season and five already in the Champions League.

The Italians will be sick of the sight of him after his hat trick in Manchester.

Speaking before the game, Guardiola said he felt his teams have a duty to entertain. Sterling was at the heart of that here in the first half -- as he has been for much of the past 18 months -- but it will be interesting to see if Guardiola takes the same approach against Liverpool.

City have not won at Anfield for 16 years, and last season's meeting on Merseyside turned into a cautious 0-0 draw. Guardiola has already insisted City do not have to win on Sunday if they want to win a third straight title but he cannot afford to lose.

Liverpool have not lost a league match since they were beaten at the Etihad in January, and a nine-point lead for Jurgen Klopp's side would be a significant advantage, even if it is only November.

A City team sent out to attack on Sunday will create chances, but it is the other end of the pitch that will give Guardiola a headache. Fernandinho has barely put a foot wrong since being pressed into action at centre-back, but a front three of Sadio Mane, Roberto Firmino and Mohamed Salah -- bursting with pace and full of energy -- presents a very specific challenge.

Fernandinho has the tactical intelligence to know, more often than not, where to be, but even that is little help when three red shirts are running at you full pelt. At 34 years old, the Brazilian is not the quickest, and he was forced to take a booking for barging Hans Hateboer when the Atalanta man threatened to race past. The space Alejandro Gomez found on the left to cross for Mario Pasalic to head in the equaliser on 49 minutes will not have gone unnoticed by Trent Alexander-Arnold and Andy Robertson, either.

"We were not as neat and tidy in the second half," said Guardiola. "We began to tire but credit to Atalanta."

With two more chances to seal their place in the round of 16, City will not live to regret a disappointing, disjointed second half in the San Siro. The same again at Anfield on Sunday will have far greater consequences.