There's also the option of playing three centre backs from Reid (if fit), Fonte, Collins and Kouyate, which worked earlier in the season. It would mean sacrificing a midfielder, but we simply can't concede three goals and expect to get anything in the Premier League.
The Hammers are missing the injured Ogbonna and still have problems at right-back, but I think Sam Byram is worth persevering with. He looks like he lacks confidence and needs assistance from the coaching staff. Sam needs help with the defensive side of his game and to be advised when not to bomb down the wing and respect he point (as he should have done at Bournemouth). But he did some good work coming forward against Leicester in the second half and is still a young player. Masuaku also looked decent going forward as a sub and is an option as a sub if Cresswell is out of sorts.
In goal Daren Randolph was caught out by Mahrez's cross and it could also be worth giving Adrian a recall, particularly if the Spaniard is better at organising his defence. Adrian, Reid, Collins and Cresswell all looked solid defenders under Allardyce, so much of the problem must be down to poor organisation. Slaven has to shuffle the team until he gets a clean sheet.