Pep Guardiola surprisingly rested the majority of his stars at the Etihad Stadium, with Erling Haaland, Ruben Dias, Bernardo Silva and Gianluigi Donnarumma all left out of the starting line-up.

Leverkusen took advantage of a dismal display from Guardiola's understudies as Alex Grimaldo put the Germans ahead in the first half before Patrik Schick netted after the break to spark grumbles of discontent from City fans at the final whistle.

For the first time in 24 games dating back 2018, City were beaten at home in the Champions League prior to the knockout stage.

It was a second consecutive loss for City after Saturday's 2-1 defeat at Newcastle in the Premier League.

City have already lost four times in the Premier League this term to leave them seven points behind leaders Arsenal.

While their first Champions League defeat in five matches shouldn't be fatal to their bid to reach the last 16, Guardiola will have absorbed the lesson that his reserves aren't quite as formidable as he would hope.

Guardiola's 100th Champions League match as City boss was a damp squib, in stark contrast to so many of the previous 99, which includes 62 wins and the club's maiden European crown in 2023.

Guardiola said he felt "embarrassed and ashamed" after his on-pitch confrontation with a cameraman in the aftermath of the controversial defeat at Newcastle.

His players should be equally chastened after this lacklustre surrender.

Guardiola had named the same team for the previous three games, but that unusually consistent selection policy went out the window with 10 changes.

Guardiola's move may have been influenced by the knowledge City face two games a week for most of December, a hectic run that includes a trip to Real Madrid in their next Champions League fixture.

- City frailties -

Nathan Ake almost put City ahead after just five minutes when the defender took Oscar Bobb's pass from a half-cleared corner and smashed a close-range effort that forced a superb tip over from Mark Flekken.

But although City monopolised possession, they lacked a killer instinct and paid for a sloppy piece of defending in the 23rd minute.

Malik Tillman and Christian Kofane were allowed time and space to tee up Grimaldo, who finished with a flourish as he lashed a low drive past James Trafford from 12 yards.

Rubbing his head in frustration on the touchline, Guardiola seemed especially vexed by Abdukodir Khusanov's leaden-footed attempt to close down Grimaldo prior to the goal.

It was the first time City had trailed in the Champions League this season and the response was far from emphatic.

Omar Marmoush struggled to fill in for Haaland, although Bobb nearly snatched a fortuitous equaliser with a deflected cross that Flekken blocked with his leg.

Tijjani Reijnders should have hauled City level on the stroke of half-time, but the midfielder shot straight at Flekken after bursting into the area.

Guardiola responded by sending on Jeremy Doku, Phil Foden and Nico O'Reilly at the interval.

O'Reilly threatened an instant impact with a long-range strike that tested Flekken.

But City's frailties in their revamped defence were exposed again in the 54th minute.

Ibrahim Maza curled an inswinging cross into the six-yard box and Schick muscled his way across the culpable Ake to glance a header into the far corner.

Marmoush failed to convert a good chance to reduce the deficit and after the Egypt forward appealed in vain for a penalty Guardiola finally introduced Haaland.

But after missing several big chances at Newcastle, Haaland drew a blank again, fluffing his lines with a poor touch that allowed Flekken to save when he should have hit the target.