Manchester City, Arsenal and Tottenham Hotspur all dropped points as Chelsea trounced Mourinho's Manchester United.
Back to drawing board for Mourinho
After a run of six matches without defeat in all competitions, Jose Mourinho appeared to be turning a corner with Manchester United, who had lost three games in succession in September.
But his team's recovery came crashing to the ground at Stamford Bridge, home of his former club Chelsea, as United fell to a scarring defeat.
A team who appeared to be growing in confidence suddenly looked entirely bereft of it, Chris Smalling and Daley Blind producing error-strewn performances in defence, Paul Pogba turning in a completely anonymous midfield display and Zlatan Ibrahimovic going a sixth league game without finding the net.
Compounding matters, centre-back Eric Bailly was forced off with what could be a serious knee ligament injury.
Changes could now follow, with club captain Wayne Rooney and under-used new signing Henrikh Mkhitaryan among those pressing for inclusion in the starting XI.
No Vardy, no problem for Leicester
Following eight games without a goal, and having been dogged by a groin complaint during the week, Jamie Vardy was left on the bench for Leicester City's home game with Crystal Palace.
Benching Vardy, emblem of last season's fairytale title win, was a gamble by manager Claudio Ranieri, whose side had gone three league matches without victory.
But it paid off as goals from Ahmed Musa and Shinji Okazaki, plus a scorching late Christian Fuchs strike, secured a 3-1 win.
Vardy entered the fray as a second-half substitute, but by that point his team-mates had demonstrated that they are perfectly capable of scoring, and winning, without him.
Stones error sign of the times
It appears Manchester City fans may have to get used to the kind of mistake that saw England defender John Stones set up Southampton's goal in the Premier League leaders' 1-1 draw when his careless backpass across the face of goal was seized on by Nathan Redmond.
With City manager Pep Guardiola determined to play a passing game and the ball-playing Stones often lauded for all aspects of his game except his actual defending, merely clearing the danger will no longer cut it at Eastlands.
As Redmond told Sky Sports: "From watching them in preparation we knew they would give us chances, they only play three at the back."
Sturridge faces winter of discontent
There was a conspicuous absence as Liverpool's forwards celebrated the second of their goals in a 2-1 home win over West Bromwich Albion.
After volleying in Roberto Firmino's cross to put Liverpool in front, Sadio Mane freed Philippe Coutinho to double the hosts' advantage.
Mane, Coutinho and Firmino, grins as wide as the River Mersey, celebrated the second goal with a lighthearted dance.
Daniel Sturridge's goal-celebration wiggle used to be a regular sight at Anfield, but he was dropped to the bench as manager Jurgen Klopp recalled the fit-again Adam Lallana to his starting XI.
Klopp appears to prefer Firmino to lead the line and when he turned to his bench for extra firepower in stoppage time it was Divock Origi who was told to get ready.
Not for the first time, television cameras caught Sturridge looking nonplussed. A long winter beckons for the England striker.
Arsenal lapse a worry for Wenger
Arsene Wenger's 67th birthday proved a damp squib as Arsenal were held to a 0-0 draw by struggling Middlesbrough.
Wenger was hoping to toast his birthday by watching Arsenal extend their winning streak in all competitions to eight matches.
But there was no celebratory drink for the manager. "When you win, you deserve it (a drink); when you don't, you need it," Wenger said.
Following their swaggering midweek rout of Ludogorets in the Champions League, Wenger had warned his players to stay humble, but this lethargic effort was typical of the stumbles that cost Arsenal any chance of winning the title in recent seasons.