Chelsea’s 2-1 victory over the Spanish giants put their Champions League ambitions back on track after a 1-1 home draw with Rosenborg, but the Ivorian striker knows that Schalke still possess the ability to upset them at Stamford Bridge.

Drogba declared: “We’ve had a difficult start so we tried to win away. We did it and now we have to focus on Schalke and it will be difficult because they have won against Rosenborg away and these two games are important to qualify as well as the next game.

“In the Champions League game against Rosenborg we had something like 30 chances and we didn’t score, against Valencia we only had three. So I don’t know, sometimes that’s football.

“If you want to score you have to believe that you will score, and it is what I know how to do best.”

But Chelsea will face Schalke without captain John Terry and left-back Ashley Cole.

Terry underwent a knee operation last week and Cole, who hurt his ankle on international duty, is expected to miss the next month with ligament damage.

The clash with Schalke will be coach Avram Grant’s first taste of Champions League football at Stamford Bridge along with newly installed assistant Henk ten Cate.

Ten Cate, who left Ajax to link up with Grant during the international break, admits it was a hard decision to make.

Ten Cate said: “Of course it was hard because I worked there with a group of very talented and very young players. The only problem with Ajax is you always lose your best players.

“Two days before qualifying for the Champions League, I lost my two best players and the club ended up with a lot of money. It is kind of frustrating. The decision to leave was a big one but Chelsea and I met at the right moment. They needed someone and I wanted to move and everything came together and everybody is happy.”

Ten Cate helped Barcelona to win the Champions League and both he and Grant share a vision to get Chelsea playing a similar style of football.

But in the post-Jose Mourinho era, Ten Cate admits the change will not happen instantly.

Ten Cate declared: “At Barcelona the first half-year was not really a success. But the people kept confidence in our work because they were seeing things improving and at the end of the season, we ended second.

“The next two years we won all the prizes to win in Spain and the Champions League which was a great result of course. But you need to be patient. You cannot do it in one year or one-and-a-half years. You have to work on this.”