Indeed, the former Arsenal midfielder feels Leicester - with their 'bundles of pace' - will cause the east London side real trouble and ultimately pick them off at Upton Park.
As such, the pundit is going for a Leicester win against the Hammers.
Merson told Sky Sports: "A top of the table clash! Both these sides had phenomenal results at the weekend but I worry for West Ham in this one. Did West Ham get it right the other day or were Arsenal poor?
"Leicester have bundles of pace... West Ham are going to have to bomb on at home, and the visitors are going to pick them off. People have been sceptical of Claudio Ranieri's arrival but they have some very good footballers at the club already. He is not attempting to build them from nothing."
The Sunderland factor
Merson has clearly attempted to apply tactical thinking and doesn't think much of West Ham's ability to control a game on the front foot. He has also tried not to overreact to one win over Arsenal.
But, in so doing, the Sky Sports pundit has inadvertently overreacted to Leicester's 4-2 win over Sunderland. Granted, Merson could well be right - but he hasn't taken into account the fact the Foxes were up against a very poor team indeed in the Black Cats. It's ironic considering he has with Arsenal...
Had West Ham faced Sunderland, who knows how many they could have scored? Leicester certainly started their Premier League campaign brilliantly but, let's face it, they are yet to come up against any sort of opposition.