Real Madrid head coach Carlo Ancelotti bemoaned one of the biggest upsets in Champions League history, the Italian believing his side did not deserve to lose to giant-slaying debutants Sheriff.

Sheriff caused a boilover at the Santiago Bernabeu, where the Champions League debutants and Moldovan visitors won 2-1 on Tuesday.

Jasurbek Yakhshiboev opened the scoring with a powerful header in the first half, before Karim Benzema's emphatic penalty levelled the scores for Madrid.

But Sebastien Thill rifled home a stunning effort from the edge of the box in the 89th minute to hand the Moldovan outfit a dramatic win in Madrid.

Los Blancos had 31 shots, hitting the target with 11, and recorded over 75 per cent possession, while Sheriff took just four shots, but came away with all three points in the Spanish capital.

The result leaves Madrid second in Group D, three points behind Sheriff, who have won their first two games in the competition.

"More than worried, we're sad," Ancelotti said after the game. "We played with intensity and were looking good. We lost because of small details, even though the side played well. We could've been better when it came to the final third but it's tough to explain.

"It's small details that cost us this game. It's a lesson for us in the future as it's a defeat we didn't deserve. We had chances, we were creating out wide and [Luka] Jovic came on and had a couple of opportunities. I think that in the end, everything went well for them and bad for us.

"We've missed out on three points and the group is wide open. We need to win our next game."

Madrid were beaten for just the second time in their last 32 group-stage games in the Champions League when playing at the Santiago Bernabeu (W25 D5) – losing against CSKA Moscow in December 2018 and Sheriff on Tuesday.

Los Blancos star Casemiro lamented the team's defensive lapses and profligacy in front of goal on a humbling night for the LaLiga leaders.

"That's football for you," Casemiro said after the full-time whistle. "One team has more than 20 shots on goal and plays well and the other team that comes here to defend and had two shots go and score twice.

"That's how things go in football and you've got to be more focused defensively. We fully dominated the game and had the chances to have made it 1-0, then 1-1 and they’ve ended up scoring a screamer.

"You've got to win in football, but this year we've already produced some poor performances and won, but that wasn't the case tonight. If you're not clinical, you end up paying the price at the back."

Madrid face Shakhtar Donetsk away from home on October 19 in their next Champions League outing, where they will seek to right the wrongs of their defeat to Sheriff.