Sam Allardyce had tacked it on, as if only an afterthought.

“It's a game for us to try to get a point in - or three,” he joked in his press conference on Friday.

Beaming like a Cheshire Cat as he shook Antonio Conte’s hand, it was an afterthought that had become reality by Saturday. Inspired by Wilfried Zaha, Allardyce’s Crystal Palace revival had claimed the scalp of the league leaders in their own back yard.

One look at Conte, his face screwed up in anger and confusion, painted a very different picture to Allardyce’s joy.

As it was, there had been a contrast between the two managers from the very beginning of this encounter; Allardyce with his feet up, pensively masticating in a club shop puffer jacket while from the first minute Conte, sleekly decked out in a black suit, was waving his arms frantically, pointing and screaming to players who could not hear a word.

Cesc Fabregas seemed to have set up a routine afternoon's work for Chelsea (Getty)

Within ten minutes they would both be on their feet though, already three goals deep in a game that rarely paused for thought.

Cesc Fabregas opened the scoring inside five minutes - though Eden Hazard deserves much of the credit - and there were already presumptions of a walkover in the East Stand of Stamford Bridge. Their afternoon would not be so leisurely.

Hazard’s would be, to an extent. When you take out the kicking and the jostling he endures, his game is very much like a stroll in the park and he continues to play at a Player of the Year level. The waltz through the right side of Palace’s defence, drilling it low for Fabregas to clip home at the near post, was the confident artistry of a player in his prime. He would create many more chances. None would be converted.

If Hazard had been the talk of the international break, with Real Madrid’s interest making the front pages again, then Zaha hasn’t been far behind.

England manager Gareth Southgate was dismissive of the winger, who turned his back on the Three Lions in favour of his native Ivory Coast and rewarded the Elephants with a wondergoal against Russia last weekend. But Chelsea could not afford to ignore him as readily as Southgate’s regime has.

Wilfried Zaha equalised four minutes after Fabregas' opener (Getty)

Zaha remains one of the best dribblers in the Premier League and, arguably, there is nobody in the division better at beating a man one-on-one. He has answered questions about his lack of end product all year, now boasting more goals and assists than Philippe Coutinho, Raheem Sterling or Mesut Ozil and, in two first-half minutes, he turned this game on his head.

First it was a goal, and one out of nothing. Taking the ball from Christian Benteke, alongside whom he was playing in a variation on a 4-4-2, Zaha turned into trouble, surrounded by four blue shirts. His low, drilled strike, however, caught them all off-guard and squeezed across Thibaut Courtois and into the far corner.

Seconds later it was two, this time Zaha turning provider for his de facto strike partner as Chelsea’s defence disappeared like grease smeared from a window, and allowed Benteke to take his time and dink the ball over a helpless Courtois.

Chelsea have made history all season but they won’t be proud of the fact that they hadn’t conceded two league goals this early in a game since 1996. Their role now was to come roaring back and show they weren’t feeling the pressure of leading the league.

Suddenly that contrast between the two managers had diminished. One, Conte, was up on his feet screaming at his players still. Allardyce was now by his side, but spent more time berating the officials.

Christian Benteke's delightful chip beat Thibaut Courtois (Getty)

It would be a long time to defend a lead at Stamford Bridge and Palace would need every decision to go their way. Chelsea would argue one did when the ball hit Andros Townsend’s arm in the penalty area but the officials waved away the hosts’ anguished screams.

The Blues were also unfortunate to find a visiting goalkeeper in form in Wayne Hennessey. The Welsh international divides opinion among his side’s fanbase – as inconsistent 'keepers tend to do.

But, at Stamford Bridge, Hennessey was outstanding. The 6ft 6in keeper seemed to get to everything that his defence couldn’t, making particularly outstanding blocks from Marcos Alonso, Nemanja Matic and, of course, the twinkle-toed Hazard.

The back four that protected Hennessey did so with increasing desperation as proceedings wore on. James Tomkins was replaced by Scott Dann at half-time, only for Dann, in turn, to succumb to injury and be removed on a stretcher after 59 minutes.

But rather than holding on to his final substitution, Allardyce rolled the dice and used his third change. Damien Delaney and Martin Kelly came on to form a back five, with winger Townsend withdrawn.

Antonio Conte's frustrations grew on the touchline (Getty)

It was an admission that Palace would be primarily looking to see this one out, rather than extend their lead. But even then, Zaha broke through on a counter and would, could or should have iced the game when one-on-one with Courtois. The Belgian’s save, with the toes of his left foot, was vital.

From then, it was all Chelsea though. Nearly thirty minutes of attack after attack, starting like the tide rippling on the beach and ending like ferocious waves crashing down on Crystal Palace’s walls.

Hazard, Diego Costa and Pedro could have done little more in terms of creating chances. Each of them was also guilty of missing them, however.

Hennessey was a blur of arms and legs as Chelsea tried every which way of finding an equalizer but he was an effective blur, keeping the arriving legions at bay.

And so with the final whistle, Sam Allardyce’s afterthought came to pass. A win from the boot of Zaha that had barely figured in the mind of his manager.

Chelsea: Courtois, Azpilicueta, David Luiz, Cahill, Pedro, Kante, Matic (Willian 59), Fabregas, Alonso (Batshuayi 74), Hazard, Costa.

Subs not used: Begovic, Zouma, Terry, Chalobah.

Crystal Palace: Hennessey, Ward, Tomkins (Dann 45 [Delaney, 60]), Sakho, Schlupp, Puncheon, Milivojevic, Cabaye, Townsend (Kelly 60), Zaha, Benteke.

Subs not used: Speroni, Ledley, Kaikai, Sako.

Referee: C Pawson (South Yorkshire)