cesc fabregas takes advantage of rob green error to win the game for chelsea three minutes from time .
chelsea had lacked a threat in the absence of diego costa and loic remy , with didier drogba up front .
before goal qpr came closest to scoring , with thibaut courtois saving well from charlie austin and matt phillips .
jose mourinho 's side are seven points clear at the top of the premier league with a game in hand .