(CNN) -- Chelsea's star striker Didier Drogba has been suffering from malaria, his club manager revealed on Tuesday, but the Ivory Coast player will still line up for the London derby against Fulham in the English Premier League on Wednesday.
Drogba started on the bench for Chelsea's 2-0 defeat to Liverpool on Sunday, having missed recent matches against Aston Villa and Spartak Moscow due to a suspected virus.
However, the results of blood tests showed that he had in fact contracted the tropical disease.
"A test showed malaria," Chelsea manager Carlo Ancelotti told his club's official website. "He lost his condition, he lost power.
"Didier had a difficulty to train because he didn't feel good, he didn't have power to train. He was unselfish to play also when he was not 100 percent."
But the Italian said Drogba was now back to health and would be fit for the league leaders' home clash with Fulham on Wednesday.
"He suffered obviously but after treatment, he will be better," Ancelotti said. "One time it was serious, now there is the possibility to treat and come back well. He is okay. Tomorrow he will play."
Ancelotti said Ghana midfielder Michael Essien would return to the Chelsea line-up, having missed the Liverpool game with a toe problem, but Frank Lampard is not yet ready to make his long-awaited return.
The England midfielder, who has been sidelined following a hernia operation, is scheduled to make his comeback against Sunderland on Sunday.
"Lampard has been training with us and he is good. He is able to play; he is fit because he worked very hard physically," Ancelotti said.
"Physically he is 100 percent -- he just has to be comfortable to play with the ball and with his teammates.'
Meanwhile, second-placed Manchester United have been hit by illness and injury ahead of Wednesday's local derby at Manchester City.
United's website reported on Tuesday that manager Alex Ferguson had yet to finalize his line-up, with several players having been sent home from training.
"So we're not in a great position at the moment. Hopefully tomorrow we're better, but there seems to be a lingering aspect of this virus going around and there's nothing we can do about it. We've a strong squad and we just carry on," Ferguson said.
United will be without injured midfielders Nani, Owen Hargreaves and veteran Ryan Giggs.
Giggs will miss a Manchester derby for the first time since making his senior debut, the UK Press Association reported, ending a club-record run of 33 appearances against City.
City boss Roberto Mancini will be without striker Mario Balotelli, who starts a three-match ban after on Tuesday failing in his bid to have the punishment reduced following his red card against West Brom on Sunday.