London - The one slight doubt about Chelsea's impressive start to the season has been that, as yet, the games they have played against other members of the Big Four have come at home. On Sunday, though, they will be tested away, as they travel to the Emirates to face Arsenal.
Chelsea stand five points clear at the top of the table - and are eight clear of Arsenal having played a game more - and have qualified for the next round of the Champions League by topping their group.
Their football has, at times, been superb, and they have battled their way to home wins over Manchester United and Liverpool, and yet they have shown vulnerability on the road against Wigan Athletic and Aston Villa.
"We are in a good moment and it is important to keep this high," said manager Carlo Ancelotti.
"The players are in a good condition mentally and we know we have a difficult game against Arsenal on Sunday but it is a good time to play against them."
Without either of their main centre-forwards, Nicklas Bendtner and Robin van Persie, Arsenal lost at Sunderland last week, and since then left-back Kieran Gibbs has broken a metatarsal.
Chelsea could have midfielder Frank Lampard back earlier than expected from a thigh injury after he underwent placenta treatment in Serbia.
"He has trained for the last two days and will train with the team tomorrow," said Ancelotti. "We hope he will be fit."
Second-placed Manchester United are away to bottom-club Portsmouth, who sacked manager Paul Hart this week.
He could be replaced by Avram Grant before the weekend, meaning the former Chelsea boss would, for the second time begin his career at an English club against Manchester United.
Sunday's Merseyside derby is a battle of two out-of-form sides. Liverpool have won just two of their last 11 in all competitions; Everton just one their last eight.
"It is a big game next against Everton and a big opportunity to improve and regain the strength we need for a long season ahead," said Liverpool midfielder Fabio Aurelio.
Manchester City, on a run of six straight draws, face a Hull City side who have benefited from a run of three straight home games by taking seven points.
Saturday evening sees the clash of two of the biggest challengers to the Big Four, Tottenham Hotspur and Aston Villa.
Villa have winger Stewart Downing in contention after he proved his recovered from a knee injury by making his debut against Burnley last week.
