Drogba is out of today's clash with Blackburn at Stamford Bridge after failing to shake off a knee injury he sustained in the 2-0 defeat at Aston Villa a fortnight ago.

The Ivory Coast striker accepts the top flight is becoming more and more competitive and Chelsea can ill afford to let their rivals steal a march on them.

Drogba told Sky Sports News: "In the league, there is a long way to go and to lose some points is not something good.

"We know what we have to do now if we want to be first and finish top of the league. I think the big teams are improving because they bought a lot of players and the league is improving and getting more difficult."

Meanwhile, Chelsea chief executive Peter Kenyon has warned the rest of Europe that Germany captain Michael Ballack is not for sale.

Ballack's absence from the Blues' Champions League squad sparked fresh speculation the midfielder would be sold in January's transfer window, with Real Madrid favourites to land him.

But Kenyon insists that is not the case, saying: "We should kill that one, not just for now but for January. There has been no discussions.

"The decision to leave Michael out of the squad is purely medical. Any suggestion it is surrounding a transfer in January is equal rubbish."

Kenyon also spelled out the reasons for Ballack's omission and said the club were working hard with medical experts from Germany and across the globe to get him back on the pitch after his ankle trouble.

Kenyon added: "There is no confusion, absolutely no confusion. The German medical team, our medical team and the player all know what the situation is.

"There's been several huge and incorrect misinterpretations going on with regards to Michael Ballack. The situation is very clear: he's injured. He's been injured for close to five months and he's still injured."

Chelsea coach Jose Mourinho confirmed he has welcomed Andriy Shevchenko back into the fold as Drogba fights to regain his fitness.

Shevchenko, who underwent groin surgery at the end of last season, has failed to figure for Chelsea so far this term.

But Mourinho scotched rumours of a rift by claiming: "It's good to have Sheva back, we need every player. We start now the period where we need everyone.

"We need to rotate players with three competitions at the same time. In the next two weeks, we have to play five matches, and that's the story we are going to have hopefully until the end of the season, so we need every player.

"He played two matches for his national team, the results were not good, but I was happy with the way he performed. He is selected and will have minutes today.

"I think his contribution to Ukraine was positive. He brought to his game some of the aspects I want him to bring.

"I was very happy watching that game. So I hope he can perform for us because we need him."