Joao Felix saw red on his Premier League debut as Chelsea's plight continued with a 2-1 loss to Fulham in the West London derby at Craven Cottage.
Ex-Blues attacker Willian broke the deadlock against his former club in the first half before Kalidou Koulibaly levelled early in the second period, but Carlos Vinicius's header 17 minutes from time sealed a well-earned success for the Cottagers.
Prior to Vinicius's winner, Atletico Madrid loanee Felix was given his marching orders after catching Kenny Tete with a dreadful high challenge, as Fulham put more daylight between themselves and Graham Potter's under-performing charges.
While Chelsea debutant Felix stole the pre-kickoff headlines as he made the starting lineup only a day after his arrival was confirmed, Fulham's final-third protagonists soon took over.
With 22 minutes on the clock, Bobby Decordova-Reid struck the crossbar with a first-time effort after being laid off by Vinicius - stepping in for suspended star striker Aleksandar Mitrovic.
The Cottagers' pressure would tell only two minutes later, as the inexperienced Lewis Hall lost the ball on the left-hand side before play switched to the right, and ex-Chelsea man Willian sought to haunt his former club.
The Brazilian twisted Cesar Azpilicueta inside and out before firing a low effort which took a deflection through the legs of Trevoh Chalobah, and Kepa Arrizabalaga could not readjust himself in time as the ball nestled into the far corner off the post.
Willian unsurprisingly refused to celebrate against his old employers, unlike the raucous crowd at Craven Cottage, who witnessed plenty of intent and duels won by their European-chasing crop.
Bernd Leno did have to be called into action on a number of occasions in the first half, though, producing two strong stops from Hall, and Felix was also denied by the German with 41 minutes gone.
Potter witnessed his side let fly 14 times without success in the first half, but they took only three minutes of the second to get back on terms, as Mason Mount's free kick from the left struck the post and Leno before falling back into the danger area, where Koulibaly prodded home.
Koulibaly's effort was caught by Leno, albeit while the German goalkeeper was behind the line, and Chelsea suddenly had their tails up until Felix's formerly impressive debut turned into a nightmare.
Only a few minutes after Denis Zakaria went off injured to add to the Blues' fitness woes, Felix went in high and with studs up on Tete in the 58th minute, and David Coote had no option but to punish the terrible challenge with a straight red card.
Despite managing to hold out for a good 15 minutes, Chelsea eventually paid the price for Felix's red card, as Andreas Pereira whipped in another delightful delivery from the right-hand side, and Vinicius's header nestled into the back of the net after Kepa's hesitation - the Spaniard initially came to meet the cross before finding himself in no man's land.
A raft of changes from Blues boss Potter did help swing the momentum in Chelsea's favour towards the end, and Leno was once again required to thwart Havertz down low in the second of six minutes of injury time.
A party atmosphere erupted at Craven Cottage as the full-time whistle blew, as Fulham rose above Liverpool into sixth place in the Premier League table - six points and four spots clear of 10th-placed Chelsea.
Marco Silva's side will aim to keep their sensational run going away to Newcastle United on Sunday, while Chelsea - who have now lost six of their last eight competitive fixtures - meet Crystal Palace this weekend.
