Chelsea's winning run in the league continued last weekend with a 4-1 victory over Cardiff City and they have a chance to make it six wins in six games against West Ham at the London Stadium on Sunday.
The match will be Maurizio Sarri's first London derby away from home in the Premier League and his Chelsea side sit top of the table ahead of match day six.
Meanwhile, West Ham have just three points from their opening five games under Manuel Pellegrini and have lost both of their first two home games of the season.
Pedro has become Chelsea's biggest concern after he left the field in the 1-0 win over PAOK with what looked like a shoulder injury. However, Sarri moved to ease worries of it being a serious injury in the post match press conference.
"I don’t know exactly the situation," he said in Greece. "I spoke for a few seconds, but it probably is not a serious injury."
Mateo Kovacic didn't travel for the game due to a dead leg that he sustained in the match against Cardiff, but he could return against West Ham on Sunday.
Ruben Loftus-Cheek returned as an unused substitute in the Europa League match against PAOK, after coming from the international break with a right tibia injury.
Cesc Fabregas made a comeback from what Sarri described as an 'unusual injury' from just below his knee, as he came off the bench in the Europa League. His return had been drastically stepped up last week and he completed 25 minutes on Thursday.Chelsea are thought to have no further injury concerns.
Chelsea have no suspensions to contend with ahead of kick off.
Chelsea potential starting line-up
Sarri faces his first major selection challenges this week as Chelsea begin to compete on three different fronts. The Europa League and Carabao Cup have created a busy schedule for the Blues, who faced their toughest away match in Europe and see a cup trip to Liverpool after they face West Ham.
This will be a test for Sarri who will need to rotate to keep his side fresh and competing on all fronts. The style of play and formation is unlikely to change, even if personnel does with a 4-3-3 formation being used exclusively this season.Eden Hazard and David Luiz were rested for the trip to Greece so they will likely come back into the side.
West Ham team news
West Ham have a number of absentees on the long term treatment table. Manuel Lanzini suffered an anterior cruciate ligament injury after being called up for Argentina's World Cup squad over the summer.
Winston Reid also suffered a major knee injury and, although he is progressing well, the match against his London rivals will come too soon. Andy Carroll is out with an ankle injury but he is back working on the pitch.
Jack Wilshere joined the injured list at West Ham for the first time after signing from Arsenal, as he requires surgery for an ankle problem.
Marko Arnautovic is expected to return after coming off in the win away to Everton at the weekend due to a knee complaint. Javier Hernandez is a minor doubt after missing the Everton match due to illness.
TV channel & kick-off time
The game kicks off at 1.30pm BST (8.30am ET) on Sunday and it will be shown on Sky Sports in the United Kingdom.
Best Opta match facts
West Ham ended a 11-game run of conceding against Chelsea at home in the league when they won 1-0 in December – they last kept successive clean sheets at home versus the Blues in August 1969.
Chelsea are looking to win their opening six games to a Premier League campaign for the third time (after 2005-06 and 2009-10) – no other side has done it more than once in the competition. The Blues have won the league on both previous occasions they’ve won their first six.
Chelsea’s Eden Hazard has either scored or assisted a goal in each of his last five Premier League appearances – he’s never done so in six consecutive games before.
Marko Arnautovic has been directly involved in 80% of West Ham’s five Premier League goals this season (3 goals, 1 assist).
Chelsea striker Olivier Giroud has been directly involved in nine goals in his 10 Premier League games against West Ham (6 goals, 3 assists) – against no side has he been involved in more in the competition.