In the space of 10 minutes, the Blues went from being in a good position to wondering if their season is over.
It was only a brief respite from the off-field ownership battle and now on-field uncertainty that brought relief at the start of the second half. The fragile state of the hosts was exposed as Christian Eriksen, Mads Roerslev and Bryan Mbuemo orchestrated a historic 4-1 win for Brentford.
Three times the Bees hit the Blues on the counter-attack from the 50th to the 60th minute with Vitaly Janelt scoring twice. They had not won since 1939 over their London neighbours, but Yoane Wissa grabbed a fourth in the dying embers of the game to guide them to their first victory.
In their first season in the top flight, this was the biggest win of the campaign and one of the most impressive. It was orchestrated through hustling and being a nuisance. They did not respect their traditional big brothers. The tactics of Thomas Frank's side were spot on as they were able to break the high press and counter- attack whenever they wanted.
Mbuemo was the only one out-ball for the Bees. In his four starts for the club, they have won three and Frank is desperate to keep him.
Frank said Saturday that Christian is a top player. He calms on the ball, finds a solution, and provides goals and assists.
While they can start to plan for next season, the immediate future of the club remains uncertain. The club is up for sale and four bids remain.
We gave away three goals in 10 minutes. I don't know why we did it. We were punished. It is a summary of strange events. We felt a bit leggy at the beginning, which is normal. Normally the goal is to open up new spaces, but the opposite happened, and I don't know why.
The build up to the match was dominated by talk of who their potential owners will be and the controversy caused by the Ricketts family bid to buy the club. The trust declared its membership "neither supports nor has confidence in the family bid for the club", in a survey.
It has been three years since Joe Ricketts apologized for making anti-Islamic comments after an email exchange was published.
The 100 or so fans outside the stadium protesting the bid were not the only ones who were against it.
Before the match, Tuchel asked supporters to make their feelings clear outside the ground, and not during the match, so as not to distract the team. He said that the team were not affected by the protests, but still it was a little eerie outside the stadium with the giant merchandise shop shut and souvenir vans lying empty.
Although the protests remained outside the stadium, it looked as if they were starting to affect the game, with Ivan Toney causing all sorts of bother and David Raya not being able to stop the well-struck attempts.
Lesser teams would have buckled if they'd gone behind, but they were able to get another gear and Janelt struck the tying goal two minutes later. Mbuemo picked out Eriksen to finish from close range for their second, and Janelt added a third over Mendy, who had struggled with a knee injury throughout the match.
Frank said that they timed it perfectly to score the four goals in front of the fans. Today everything clicked, even though you don't get what you deserve. It was almost a complete performance to win here at the Bridge against the Europeans. It was a big moment for the club and we were brave, pressed high.
The Brentford fans were lapping it up in their corner of the stadium as the other fans were quiet. They went through their full catalog of songs, and the third brought a self-deprecating song about Queens Park Rangers fans.
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