Both London clubs have lost their opening two matches of the Premier League season and any chance of a revival under new manager's look as though they'll take some time.
Emery searching for first win
Life in England has been a steep learning curve for Arsenal's new Spanish head coach, Unai Emery.
Matches against the last two title winners haven't told us a great deal about what the Gunners are capable of this season, but there are signs of a new philosophy and style embedded within the North London club.
Passing out from the back caused havoc against City on the opening weekend and at Stamford Bridge, they also faced difficulties in defence.
Arsenal failed to create in their 2-0 defeat to Pep Guardiola's men, but it was polar opposite against Chelsea. They should have been 5-2 up at half-time had it not been for some sloppy finishing from the usual cool head in front of goal, Pierre Emerick-Aubameyang.
There isn't a worry about attacking play though, and at times Emery's philosophy of playing out from the back worked tremendously well - which was evident in Alex Iwobi's equalising goal against Chelsea.
Arsenal should, therefore, relish a chance to play easier opposition on Saturday. West Ham have already shipped four goals against Liverpool this season and were also poor defensively against Bournemouth.
The Gunners have received perhaps more criticism than most this season, which is difficult to grasp considering their first two matches. Henrikh Mkhitaryan who scored against Chelsea, hit back at critics in the week.
"We have a new manager and are trying to adapt to his philosophy and also his demands," the Armenian said.
Mkhitaryan also added: "I don't know why people are criticising so much. I'm not paying attention because I know if I've played bad or well."
Pellegrini also struggling
West Ham have not had an easy ride so far this season either. A new chapter under former Premier League winner Manuel Pellegrini brought excitement to the Hammers over the summer - and after an impressive transfer window, there was plenty of optimism.
However, two poor performances in the opening weeks of the season and a layer of doom and gloom has appeared over the East End of London again.
The Hammers' new signings are yet to hit the ground running and there are defensive issues once more.
But there may be no better time to face Arsenal this season than in the early weeks whilst they're still learning Emery's system.
That being said, both teams are trying to accommodate to what their bosses want from them, and like against Chelsea with Maurizio Sarri, the Gunners could be a part of another very open game.
West Ham's side will bolster Jack Wilshere who finally left Arsenal permanently in the summer after over a decade at the club.
Wilshere was hotly tipped at Arsenal before a succession of long-term injuries hampered his progression. Although he featured regularly last season, he took the decision to move on for the good of his career.
Discussing the midfielder in his pre-match press conference, Emery revealed: "I spoke with him for 15 minutes here at Colney before he left."
Although Wilshere was set for a new contact on a lower salary, Arsenal's new head coach made it aware to Wilshere that his playing time would be limited should he stay with the club.
“Our conversation was very clear. For me, one thing is important for him - to be a protagonist in a new project." Emery asserted.
Wilshere may not be the only Gunner returning this Saturday, with Arsenal having sold Lucas Perez to West Ham in the transfer window too.
Arsenal have no fresh injury concerns going into this weekend's clash at the Emirates.
Laurent Koscielny returned to the training ground in the week to continue his rehabilitation but won't resume full training for another couple of months. Ainsley Maitland-Niles and Sead Kolasinac remain out.
Mark Noble is a doubt for West Ham and therefore Pedro Obiang could form a midfield pairing with Wilshere in his absence.
Andy Carroll and Winston Reid are still out with injury, whilst Manuel Lanzini remains on the sidelines having torn the anterior cruciate ligament in his right knee before the World Cup.