Arsene Wenger is reportedly considering a return to four in the defence, after the injuries to Shkodran Mustafi and Aaron Ramsey.
Ramsey is out for the next couple of weeks due to a hamstring injury he picked up in the 1-1 draw with Southampton on Sunday. Mustafi is also set to miss out, which could force Wenger to opt for just two centre-backs rather than three.
According to the Telegraph, Wenger could field a back four against West Ham, with a defensive midfielder like Francis Coquelin coming in for Ramsey alongside Granit Xhaka, and another attacking player replacing the centre back.
This might rule out Jack Wilshere starting, unless Wenger plans to have the Englishman in a more advanced role, as he has done in the Europa League and Carabao Cup this season. We could also see Alex Iwobi or Danny Welbeck get a start on the right flank.
Mustafi absence could force Wenger to name Laurent Koscielny and Nacho Monreal as a defensive partnership, if he doesn’t trust the ageing Per Mertesacker, inexperienced Rob Holding and Calum Chambers to call on.
A tactical shift would mean a 4-2-3-1-looking formation, with Mesut Ozil behind the lone striker is the No.10 position, and Alexis Sanchez on the left.