There is one player at Chelsea who has come to epitomise the health of the club’s title challenge more than any other in recent years and that is Didier Drogba.

For all of captain John Terry’s leadership qualities, it is the Ivory Coast international who provokes most fear in the club’s opponents with the manner in which he can bully defenders.

If the striker is firing on all cylinders the team’s fortunes tend to be on an upward curve.

Conversely, the side often suffer dips in form should he hit low points.

With the benefit of hindsight, it is no surprise that Chelsea’s woeful slump in form before Christmas, which triggered a measly collection of 10 points from 11 games, began the moment Drogba was diagnosed with malaria in November.

The illness isn’t contagious but, without their talisman in good working order, a different disease spread among his team-mates. they also seemed somewhat weaker and under the weather.

There appeared to be no cure for those symptoms as Chelsea suffered defeat after surprising defeat. however, one fearsome strike with Drogba’s right foot at the Reebok Stadium has provided the club’s championship challenge with the medicine they so desperately need. some signs of recovery had been spotted this month with successive wins at home against Ipswich and Blackburn but the goal which has sent a real message to the rest of the Premier League was Drogba’s 30-yard effort past a bewildered Jussi Jaaskelainen.

It not only put Carlo Ancelotti’s side on course to secure their first away win for three months, it generated a spark in the Blues’ play not seen for several weeks. While Drogba spent the rest of the game making a mockery of Gary Cahill’s ?20million price tag, suddenly Florent Malouda, Nicolas Anelka and Michael Essien looked like their old selves and raised their game, too.

Chelsea may have scored four but it could have been double that. Before Terry emerged out of the dressing room to give his usual battle cry following the final whistle, the team blasted upbeat songs out of a stereo loud enough for anyone in Manchester, let alone the Bolton dressing room, to hear.

As the players emerged, frowns had clearly been replaced by smiles. There is no doubt they are now looking up the table at leaders Manchester United rather than over their shoulders and the threat of Tottenham taking their Champions League place.

Many will argue they have left themselves with too much ground to make up, with Sir Alex Ferguson’s men having the chance to go 10 points clear if they beat Blackpool tonight.

Yet while Drogba’s malaise robbed them of their customary consistency, his renaissance now offers them renewed hope. As Terry said: “I think he is over the malaria now. I have never had it myself but speaking to people and the doctor here, it does knock you for six. fair play to him, he could have taken two months out but he never, he wanted to keep on fighting for the team.

“He knew we were lacking in options in the whole squad and he wanted to put his body on the line for the club. we really appreciate that.

“He has taken a bit of stick as we all have over the past few months but we have stayed together. we know that he is capable of goals like that, and many more. we are just encouraging him to shoot more and get the ball out of his feet. Our confidence, not just his, will get a lift and we’ll crack on. I think we all looked more like our old selves.”

There are more stiff tests to come, with a trip to Everton in the FA Cup on Saturday before Premier League matches at Sunderland and then home to Liverpool. It was defeats by the latter duo in November which first highlighted the extent of Chelsea’s problems, especially as an attacking force without Drogba being on song.

Still, the last time the former Marseille star suffered a quiet first half of the season in a Chelsea shirt, he almost singlehandedly fired them to the semi-finals of the Champions League in 2009.

Back then it was a knee injury, as well as an uneasy relationship with then boss Luiz Felipe Scolari, that kept him subdued, only to spark into life following Guus Hiddink’s arrival at Stamford Bridge as the new coach.

As it stands, the swerving effort which proved too good for Jaaskelainen last night was his 10th of the campaign, which isn’t bad by most forward’s standards, although not quite matching the pace he set last term when he finished with 37.

With Malouda and Anelka getting on the scoresheet once again last night, as well as Ramires netting his first since joining from Benfica in the summer, the squad are not looking so weak as many have claimed.

Indeed, with Frank Lampard expected to return from a calf problem – which caused him to sit out this match – at the weekend and David Luiz set to join from Benfica, coach Ancelotti appears to have good reason to be optimistic.

As Terry added: “Southern softies? People may have that impression but we’re not. you can see against Bolton that we can mix it with them.

“On their day Bolton can play very good football but when they do put it in the box we have people like Branislav Ivanovic, myself and Didier and we’re ready to fight, which is key as well.

“We’ll certainly see [if the belief is back] because we have some tough games coming up. “It is going to be a big test, we realise that, but we’re certainly up for the fight and we won’t give up.”