LONDON - English Premier League Champions suffered a nightmare start to their title defence, having two men sent off as Burnley claimed a superb win at Stamford Bridge.
It would be easy but misleading to lay the blame for Chelsea defeat on the decision to show a red card to new club captain Gary Cahill for a lunging tackle on Steven Defour midway through the first half.
But that would deprive Burnley their due for a disciplined, energetic and ruthless first-half display that saw them score three times, with Sam Vokes netting twice - a header and a volley - either side of a lashing angled drive from Stephen Ward.
The Blues were better after the break and pulled a goal back when summer signing Alvaro Morata headed in shortly after coming off the bench.
However, the Spaniard was also at fault for denying the home side a second goal, adding an unnecessary touch to Andreas Christiansen's goal-bound shot from an offside position.
Chelsea's hopes looked to have gone when a late challenge from Cesc Fabregas on Jack Cork added a second yellow to his first, received for dissent, to leave the Blues with nine men.
But David Luiz fired home from inside the box after being set up by a Morata header to set up a frantic final few minutes, during which Burnley struck the post through Robbie Brady before holding on to take the three points.
It has been a difficult summer for Chelsea and their boss Antonio Conte, who has openly voiced his frustration at the club's failure to recruit his desired targets - both in terms of quality and quantity.
This game felt like the culmination of such issues and could well be the breaking point that leads to further significant moves in the transfer market.
Attacking midfielder Jeremie Boga is undoubtedly talented but his inclusion - along with a a bench populated largely by inexperienced young players - also felt like a point being made about the resources the Italian has available.
There was no Diego Costa (on his way out), no Eden Hazard or Pedro (injured) and, after 24 minutes, no Cahill, exposing the decisions to let Nathan Ake join Bournemouth and fellow defender Kurt Zouma go on loan to Stoke.
Cahill's red card ended Boga's shock debut early, as he was replaced by Christensen, and handed the initiative to Burnley, whose three-goal salvo added disbelief to the list of negative emotions ripping through the home support.
On the plus side for the Blues, Morata adapted quickly to life in the Premier League, showing an intelligence of movement and eagerness, even if this did lead him to deny his side a goal.
But Conte has plenty of thinking to do. This was the Blues' first opening-day league defeat since 1998 and they have now had four men sent off in their last three competitive games, dating back to last season's FA Cup final.