NICOLAS Anelka's first-half header helped Chelsea tighten their grip at the top of the table with victory over Bolton.
The Frenchman met Didier Drogba's teasing cross to bag the only goal of the game two minutes before the break at Stamford Bridge.
But it was the visitors who came closest to breaking the deadlock early on when Petr Cech spilled a cross, only for Alex came to his rescue to clear Matty Taylor's goal-bound effort.
However, the hosts hit back, Drogba's curling free-kick was beaten out by Jussi Jaaskelainen against Salomon Kalou, but the ball drifted agonisingly wide.
Chelsea's leading scorer missed a gilt-edged chance moments later when he failed to connect with Anelka's cross, while he also flashed a free-kick wide.
But the Blues eventually took the lead on 43 minutes when Drogba sent the ball over for Anelka to head home from close range.
Kalou missed a great chance to double their lead early in the second-half when he shot straight at Jaaskelainen, while the giant Finn denied Chelsea again minutes later , this time keeping out Zhirkov's rasping drive.
Frank Lampard did eventually beat the Bolton keeper, only to see his 20-yard strike shot bounce back off the inside of the post.
They were almost made to pay for their catalogue of misses late on, as Cech could only watch on as Ivan Klasniv's shot flashed across his goalmouth.
Sub Joe Cole fluffed his lines from four yards in injury-time, but Chelsea hung on to go four points clear at the top.