Ruud van Nistelrooy's Leicester hit a new low as Brentford thrashed them 4-0 at home to make it seven games without a win at the King Power Stadium.
Foxes fans either booed or streamed for the exits after half an hour as the Bees raced into a three-goal half-time lead thanks to a 15-minute flurry.
The superb Mikkel Damsgaard set up Yoane Wissa and Bryan Mbeumo for classy goals, before the latter crossed for Christian Norgaard to head home a free-kick.
Were it not for Kevin Schade's header hitting the woodwork and Keane Lewis-Potter's disallowed goal for handball, it could have been worse.
"It's been awful. Leicester seem lost on the pitch," former Foxes captain Wes Morgan told Sky Sports at half-time. Ex-Leicester striker Alan Smith added: "There are many Leicester players who don't want the ball and when they do, they don't know what to do with it."
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Brentford only needed first gear for the second half as the rain began to thump down - giving more home fans another reason to leave. The biggest cheer from the Foxes supporters all night were ironic ones as fan favourites Stephy Mavididi and Facundo Buonanotte came on early in the second period.
Despite easing off, Brentford still added a fourth when Fabio Carvalho netted late on after more good work from Mbeumo.
Credit should go to Brentford, who secured not only their first back-to-back wins of the season but also a club-record fourth straight Premier League away victory. They had failed to win a single game on the road this season before this run, which brings them into the race for Europe.
For Leicester, it was a sixth home game in a row in which they have failed to score. Their last home goal came on December 8 against Brighton.
Player ratings:
Leicester: Hermansen (3), Coulibaly (4), Faes (4), Okoli (3), Kristiansen (4), Soumare (4), Ndidi (5), El Khannouss (5), Decordova-Reid (2), Vardy (6), Ayew (4).
Subs: Vestergaard (6), Mavididi (5), Buonanotte (6), Coady (n/a).
Brentford: Flekken (7), Ajer (7), Collins (8), Pinnock (7), Lewis-Potter (8), Norgaard (7), Janelt (7), Damsgaard (9), Mbeumo (9), Wissa (8), Schade (7).
Subs: Yarmoliuk (6), Carvalho (6), Maghoma (6), Kayode (n/a), Konak (n/a).
Player of the Match: Mikkel Damsgaard (Brentford)
WATCH: All the goals as Leicester fans boo their own team!
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Ruud: A huge step back
Leicester manager Ruud van Nistelrooy to Sky Sports:
"We have to acknowledge that it's a huge step back. There was hope after certain performances. The beginning of the game was hopeful with three chances, Jamie [Vardy] had two and [Woyo] Coulibaly had a shot from close range, where we have to go [one] up. That could have changed the game.
"But the first goal from them was really efficient. It was a well-organised team with great physique. In the end, after the bright start, we were never in the game. Then the game was done.
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"Overall, the difference between the level of Brentford and us today was big. The first 10, 15 minutes, after that they showed they were big steps ahead of us at the moment.
"We were nowhere near their levels today. We have to acknowledge it. The level between Brentford and us was significant today - and a worry for future hopes.
"I feel we are better than what we showed today. Efficiency - first, second and third chances for them were all in. That's the difference between us and the other clubs.
"Also we know we gave the other teams above us and below us the chance to gain points and momentum. Then it can become difficult really quickly if we don't keep picking up points."
Analysis: Morgan on 'terrible' and 'frail' Leicester
Former Leicester captain and Premier League winner Wes Morgan on Sky Sports' Friday Night Football:
"There's a real frailty, not just in the defence but the whole team. It showed, conceding the type of goals they conceded in the first half.
"Before Ruud took over, the fans weren't totally happy with the performances or the position. He got a reaction straight away but it's never been consistent and the recent run of form has been terrible.
"Looking at the positives, it's only two points [behind 17th-placed Wolves]. But the stats, the form, the confidence, everything is pointing down. That's got to change.
"It's been proven it can be done. I was part of a great team which escaped our first season back. I'm sure the fans are going to be disappointed with how things have gone in recent weeks but things can change - they know what's happened in the past.
"The fans just have to stick with the team, get behind them and be positive. It's not too late, there's plenty of games to go. They just need to find that one game, that one spark, to turn things around."
Frank: Winning two games in a row is strange!
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Brentford manager Thomas Frank to Sky Sports:
"I think we've been fairly consistent in performances. We had one terrible, bad one to Fulham in the early stages of the season. This is the first time we've won two games in a row, it's a little bit strange!
"We are in an upward curve and hopefully we can continue that.
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"I would go so far to say it's a front four! Mikkel Damsgaard is the one that really gets them going.
"The front four, the way they interact, the relationship, the more they play, they have all the ability we need.
"A big thing is that he is fit. The first season he came back for being out for almost a year, he had to get up to pace. The second season, he was four months out. Now we have a rhythm, he's clicking with the team, it's nice to see.
"It's not easy to win in the Premier League, it's not easy to win away. It's not easy to win 4-0 away.
"I know Leicester are not in a good way but Arsenal were here a few days ago and they only won 2-0."