Chelsea have extended their lead at the top of the table to four points after a narrow 1-0 win over Bolton Wanderers.

Nicolas Anelka scored his first goal since January as the Blues took advantage of their game in hand over title rivals Manchester United to put themselves in the box seat for the Premier League crown.

Sir Alex Ferguson had labelled Tuesday's clash at Stamford Bridge as 'easy' for Carlo Ancelotti's side but the hosts found the Trotters tough to break down in the opening stages.

Indeed it was the visitors who could have taken a first-half lead when Didier Drogba handled in the box midway through the opening period, only for a penalty not to be awarded.

Chelsea broke Bolton's resolve just before the break as Drogba teed up Anelka for the easiest of headers to open the scoring against his former club.

If Trotters boss Owen Coyle was angry about Lee Probert's refereeing on the Drogba incident, he will tear his hair out after the official's failure to give a penalty for John Terry's handball in the area from Lee Chung-Yong's cross in the second half.

But it was not to be for the Wanderers, who remain five points clear of the drop zone after being sunk by their former striker.

There was little evidence that Chelsea would struggle to overcome Coyle's side when left-back Yury Zhirkov created a chance for the home side in the fifth minute.

The Russian pulled the ball back for Ivory Coast striker Drogba who sent his curling shot over the crossbar.

Bolton's defence was almost caught out again moments later but Drogba was given offside as he tried to beat Jussi Jaaskelainen.

Scare

In the seventh minute, Chelsea had a scare when captain Terry required lengthy treatment on his ankle following a collision with Matthew Taylor. But the England defender was able to continue without any ill effects.

The Blues had lost their early impetus, though, and Bolton caused problems for the home side when Petr Cech failed to collect a cross from Lee.

Taylor almost profited from Cech's hesitation but the Czech Republic international quickly regained control of the ball before the Bolton midfielder could strike.

Zhirkov was in the wars in the 18th minute when he went down following a collision with Bolton striker Kevin Davies. The left-back required a hefty bandage on his head to stem the flow of blood before being allowed to continue.

Chelsea almost went in front in the 25th minute when Jaaskelainen punched Drogba's free-kick straight at Salomon Kalou. But, luckily for Bolton, it bounced off his head and wide.

The hosts were becoming more and more frustrated by Bolton's battling rearguard and that increased in the 37th minute when Drogba sent another free-kick wide of the target from 20 yards.

Zhirkov was asked to leave the pitch in the 39th minute by referee Lee Probert because he was still losing blood from his head wound.

It was clear the Russian defender's injury required stitches and Chelsea continued with 10 men - Frank Lampard taking over Zhirkov's position until he re-appeared in the 41st minute.

Breakthrough

The breakthrough came in the 43rd minute when Drogba's cross was headed home from inside the six-yard box by Anelka.

It was the France international's first goal in 14 games for the Blues in a barren spell lasting just over two months.

Moments later Kalou tried to increase Chelsea's lead but his 20-yard shot was well wide of the target.

Chelsea's opening goal failed to liven up their performance as the second half began.

Bolton enjoyed much of the possession and the home side looked decidedly subdued.

Chelsea had even resorted to lumping high balls in the general direction of Drogba but it was a fruitless tactic.

Kalou wasted a great chance to put the game beyond Bolton in the 54th minute when Drogba put his Ivory Coast team-mate through on goal.

Kalou only had Jaaskelainen to beat but his shot was saved by the Bolton goalkeeper.

Penalty appeal

But it was a rare chance for the home side, who then survived a penalty appeal when Terry appeared to use his arm to divert a cross from Lee into Cech's hands.

Zhirkov forced Jaaskelainen into another fine save when he collected a return ball from Lampard and thumped a volley straight at the Bolton keeper.

Anelka was replaced by Florent Malouda midway through the second half.

A superb 40-yard pass from Alex in the 75th minute allowed Kalou to get free of the Bolton defence yet again but his angled drive was well saved by Jaaskelainen.

Three minutes later Lampard almost sealed victory when his 20-yard drive cannoned back off the inside of the post.

Six minutes from time Bolton substitute Johan Elmander was inches away from equalising when he headed a cross from Taylor just wide.

It was, though, the last nervy moment for the hosts, who hung on to move a step closer to achieving the league and FA Cup double.

Chelsea	Team Statistics	Bolton Wanderers
1	Goals	0
1	1st Half Goals	0
8	Shots on Target	0
13	Shots off Target	8
0	Blocked Shots	4
5	Corners	2
13	Fouls	22
2	Offsides	3
1	Yellow Cards	4
0	Red Cards	0
81.4	Passing Success	61.3
20	Tackles	28
60	Tackles Success	60.7
62.9	Possession	37.1
48.8	Territorial Advantage	51.2

Teams

Chelsea  Cechl, Ferreira, Alex, Terry, Zhirkov, Ballack, Mikel, Lampard, Kalou (J. Cole 77), Anelka (Malouda 67), Drogba
Subs Not Used  Hilario, Deco, Sturridge, Bruma, Van Aanholt
Booked  Alex
Goals  Anelka 43

Bolton Wanderers  Jaaskelainen, Steinsson, Cahill, Knight, Robinson, Lee (Klasnic 82), Muamba, Ricketts, Taylor, Wilshere (Elmander 82), K. Davies
Subs Not Used Habsi, Samuel, M. Davies, Cohen, Weiss
Booked  Steinsson, Robinson, K. Davies, Elmander
Goals 

Attendance 40,539

Referee  L. Probert