The peripatetic France striker seemed like a stop-gap and few expected him to be part of Chelsea's long-term future.
He had just spent 18 months at Bolton Wanderers after spells at Fenerbahce, Manchester City, Liverpool, Paris St Germain and, following the best piece of business in Arsenal's history, Real Madrid who he joined for 23 million pounds.
At none of those clubs, however, did he really settle and deliver the regular match-winning performances that made him such a deadly proposition under Arsene Wenger at Arsenal.
His first half-season at Chelsea produced just two goals and, although he was far more prolific last term with 25 and some excellent displays, there was always the feeling he was second fiddle to Didier Drogba.
This season, however, Anelka seems to have stepped up a gear and gives the impression that not only is he enjoying his football, a rarity for a man nicknamed 'the incredible sulk' , but he is increasingly the focal point of Chelsea's attack.
He headed the only goal on Tuesday in the Champions League win at Porto that secured top spot in Group D to maintain his record of vital goals this season having been the sole scorer in the home win over Porto and 1-0 victory at APOEL Nicosia.
He was also outstanding for France in the 1-1 playoff draw with Ireland that secured a World Cup berth, holding the ball up repeatedly with a sure touch and keeping possession despite some tough Irish tackling that previously might have seen him wilt.
"Not only in the Champions League but in all competitions Anelka is having a very good season," Chelsea boss Carlo Ancelotti said after Tuesday's win.
"He is a very important player, sometimes playing as a striker close to Drogba, sometimes helping the midfield. His position is very important for our play."
On Sunday Chelsea face London rivals Arsenal, where Anelka made his name as a teenage tyro after being nabbed from PSG for a bargain 500,000 pounds by Wenger.
He scored there in last season's impressive 4-1 triumph and any sort of repeat would be a huge help in Chelsea's title push.
"It is a very good time for us and we have to keep this going because the players are in good condition, have a good mentality and want to maintain this momentum," Ancelotti said.
"We know very well that Sunday will be a very difficult match but we know that now is a very good time to play Arsenal," he added, with their opponents hit by a string of injuries.
Chelsea could be further boosted by an early return for Frank Lampard after a thigh strain. Ancelotti said the England midfielder was in full training and may be fit for Sunday.
