Ranieri's struggling champions slumped to a 2-0 defeat against Everton on Monday.
Ranieri's struggling champions slumped to a 2-0 defeat against Everton on Monday which kept them just three points above the Premier League's bottom three.
And although Ranieri was without suspended striker Jamie Vardy, Mahrez, last season's PFA Player of the Year, didn't even make the starting line-up at the King Power Stadium.
It was a far cry from last term when everything Mahrez touched turned to gold during Leicester's fairytale title triumph.
Ranieri explained the winger's omission by demanding he give more for the Leicester cause.
"Because he's not in good form now and I wanted to stimulate him," Ranieri said when asked why he was left out.
"I didn't see him do well during the training sessions and he must give more for the team. I want more."
Leicester face a rejuvenated West Ham on Saturday with tensions rising around the King Power Stadium.
Ranieri had predicted a tough campaign back in September, although the reality of a relegation dogfight is biting hard.
"If you remember well, I think three months ago, I told everybody we are in the battle but I want to fight and I want to stay very concentrated on the little details," he said.
"The little details are like the first goal, to react early."
Ranieri will have been dismayed by the manner of Everton's goals, scored by Kevin Mirallas and Romelu Lukaku.
Mirallas' strike was especially bad as it came from a huge punt up field from goalkeeper Joel Robles which put the Belgian striker clear of the two centre-backs.
Three touches is all it took and the ball deflected into the net off Marcin Wasilewski.
"We reacted a little late from the long kick but that is football," Ranieri said.
In contrast, Everton boss Ronald Koeman was full of Christmas cheer as he hailed the defensive spirit of his team in their first away win since September.
"The team organisation defensively was outstanding," Koeman said.
"Maybe they had one chance with a free header but it was not really a big chance.
"Idrissa Gueye (had) a fantastic opportunity to kill the game and finally Romelu did but it was important also to have a clean sheet for confidence. We showed the aggression in the performance that we want."
As for the rather direct nature of the goals, Koeman explained it had all been worked out on the training pitch.
"We like to play from the back but if the opponent is pressing then we don't take risks," he said.
"Finally in the last part of the second half they did more pressing and then you need to play the long ball and you need to push up and you need to fight for second balls.
"I think we won a lot of battles in the second half which was good and then you make it very difficult."
Lukaku had been a virtual bystander until his late clincher, with Koeman having to tell the Belgian to exert less energy in areas where he wasn't so effective.
"My message to him at half-time was to say to him: 'Sometimes you run too much. Stay in front, stay between the two centre-backs and for crosses you need to be in the box,'" Koeman added.
Whether it was an angry protest or a piece of festive fun following their failed appeal to release Vardy from his three-match ban for his sending off against Stoke, 30,000 Vardy masks were placed over the seats of the stadium.
Ranieri, tactfully, said he did not see the masks and could therefore not comment on whether it was aimed as an anti-FA statement.