Pep Guardiola took the blame after his selection gamble backfired as under-strength Manchester City suffered a shock 2-0 defeat against Bayer Leverkusen in the Champions League on Tuesday.

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 to 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.

"I take full responsibility, still I think the players that started were exceptional players but we missed something needed at the highest level," Guardiola said.

"I have to accept it. It belongs to us. If we win it wouldn't be a problem so I have to accept it that maybe it's a lot of changes.

"I think playing every two or three days we need to make changes but seeing the result, maybe it's too much."

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.

The 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.

"We had more chances than them, but they were half-chances. We now have to fight for the next games," Guardiola said.

- 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.

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 Tijjani Reijnders should have hauled City level on the stroke of half-time when he straight at Flekken after bursting into the area.

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

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.

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