Crystal Palace manager Alan Pardew described Chelsea as ‘unbeatable’ in the run-up to Saturday’s Premier League clash. It may have been an attempt at reverse psychology, but, after seeing his side succumb to a 1-0 home defeat, Pardew was left to reflect on the accuracy of his words.

Palace did little wrong against Premier League leaders Chelsea. In fact, Diego Costa’s headed goal just before half-time with Chelsea’s first shot on target. However, once that goal went in, Antonio Conte’s side never looked like letting Palace back into the game.

Remarkably, the win over Palace was Chelsea’s eleventh league victory in a row.

That equals a club record and is only three shy of the overall Premier League record, set by Arsenal in 2002. Chelsea are now nine points clear at the top of the league, albeit having played a game more than their nearest rivals.

Costa looks unstoppable

The form of striker Diego Costa is arguably the main reason behind Chelsea’s table-topping efforts this season. Costa’s deciding goal on Saturday was his thirteenth of the campaign so far, making him the league’s top scorer. He already has more Premier League goals this term than he managed across the entirety of last season.

His importance to Chelsea is plain for all to see. Looking at the past four games, he netted the only goal on Saturday, scored a late winner in a scrappy 1-0 win over West Brom and contributed a goal and an assist in a match-winning display against title rivals Manchester City.

Costa defined Chelsea’s powerful performance at Pep Guardiola’s City – a victory that was reminiscent of Leicester’s in their title-winning campaign.

Clearly, Costa is not the only reason for Chelsea’s success. Eden Hazard has looked similarly revitalised this season, while the Blues’ defence is starting to appear impregnable.

Conte’s decision to switch to a back three after going 3-0 down at Arsenal has proved to be inspired. They have since won 11 games on the bounce, conceding just two goals in that time.

A changed man from last year

While Chelsea’s superb start to this campaign has been a team effort, no-one epitomises their transformation like Costa.

He was largely disappointing last season – few Chelsea fans would have minded if he had been sold for a sizeable fee over the summer.

That sounds ridiculous to say now, but if we journey back a year everything was very different for Costa and Chelsea. On December 17, 2015, Jose Mourinho was sacked as manager after an abysmal start to the season. Chelsea were in 16th place at the time, having suffered nine defeats in 16 league games. It was a dramatic fall from grace for Mourinho and Chelsea – they were crowned champions just seven months earlier in May 2015.

Mourinho’s reputation was understandably damaged (he still appears to be struggling to rediscover his former self at Manchester United), but Chelsea’s players did not escape blame.

Costa was targeted in particular, amid reports that he returned for pre-season training that year unfit. Many accused him of growing disinterested and ‘downing tools’ on Mourinho.

He has clearly taken that criticism to heart, and may well be using it as motivation for his sublime form this season. Provided he keeps playing like this, both he and Chelsea will be in the headlines for only positive reasons this season.