1-0 and up a man for Sean Dyche's visitors.
Spurred on by Cahill's dismissal, Burnley surged into a 3-0 half-time lead at Stamford Bridge courtesy of two goals from Sam Vokes either side of a spectacular Stephen Ward strike, and Chelsea could not salvage a draw despite a debut goal for Alvaro Morata and David Luiz's volley in the second half.
A few minutes after, Burnley piled more misery on Antonio Conte's wards, when S.Vokes found the net.
Conte will have some thinking to do, along with the board, as both Cahill and Fabregas will be missing for next week's match with Tottenham Hotspur.
Manchester City clear favourites for Premier League title
But there were too many draws. " At the end of the game the boys were disappointed that we didn't win ". Leaping from sixth place to top may appear ambitious but United are precisely that.
Stamford Bridge was stunned.
That was until Luiz sprinted onto Morata's pass and volleyed in to bring the nine men to within a goal of Burnley.
With Champions League football to contend with this season, the absence of proven goal scorer Diego Costa and injuries to others including star man Eden Hazard, their squad is looking dangerously thin.
Marcos Alonso's long-range drive was tipped over by Tom Heaton as Chelsea registered their first shot on target early in the second half, while Morata came on to replace the ineffective Michy Batshuayi in attack. He will need some help from his owner otherwise Chelsea really do risk having another "Mourinho season".
Arsenal set to offer bumper contract deal to Sanchez
The France worldwide came off the bench to head home in the 85th minute as Arsenal started their season with a thrilling 4-3 win. Ten minutes after the restart saw the host go behind yet again as Vardy who was unmarked headed a corner from Mahrez in.
As well as worsening Chelsea's predicament, the Spaniard's dismissal marked the first occasion ever on which two players from the same team had been sent off on a Premier League opening day.
Conte cut an unhappy figure on the sideline, as he has done during most of pre-season and at Wembley last weekend. Still, the game had barely got out of second gear when Cahill received a straight red in the 14th minute for a high challenge on Steven Defour.
Cahill was made club captain following the departure of long-serving skipper John Terry at the end of last season. The biggest threat for Burnley is that a bigger club comes in and poaches him. They still had the quality to peg Burnley back, particularly as the visitors exhausted as the second half wore on, but lacked subtlety in their approach.
Chelsea had their first real chance at goal 11 minutes in when Cesar Azpilicueta's low cross was deflected and almost sat up for Willian to fire home in the centre of the goal.
Pentagon Ready to 'Fight Tonight' as Tensions Between US, North Korea Escalate
As the insanity increases and the threats between the US and North Korea escalate, might I make a suggestion. Pacific Command showing B-1B Lancer bombers on Guam.
Despite the dire performance, the majority of the 41, 616 fans still cheered head coach Antonio Conte's name from the stands.