The Belgium international has been a revelation since his arrival from Ajax in the summer.
Vermaelen said: "Of course Chelsea is number one in the League so it's a big game. There's a little gap between us now so for us it's important to win this game.
"I've seen them a few times and of course you know all the players and their qualities.
"Because there is already a gap, it's important to win. If we lose though I still think we can win the league, it's not a big problem.
"We're always confident at home and we have to continue that against Chelsea."