Merson critical of Tottenham's recent performance.
Spurs could only draw 1-1 against the Baggies, and have now taken just one point from their last two league games.
Merson told SkySports that he felt Spurs are too reliant on Christian Eriksen, and picked out three players he feels are incapable of stepping up.
He said: "A shocking result for Spurs on Saturday. I just think with Tottenham that if teams do not have a go at them, they struggle.
"If you do not have a go at them and just sit back into shape, they do not have anybody who can break you down.
"Harry Winks is not one of those players who is going to put a ball through an eye of a needle, nor is Eric Dier and Dele Alli is better running off the ball. So they just have Christian Eriksen and if he has an off day, I just do not see where it happens for them."
Tottenham face Leicester City in midweek, a team they demolished 6-1 away from home in their last visit.
The Foxes are better defensively this season, and have new manager Claude Puel overseeing their improvement.
But this is a game Tottenham need to win, already 13 points behind league leaders Manchester City, they have slipped into fifth place behind rivals Arsenal.
They need star man Christian Eriksen back to his best quicker than ever.