The 36-year-old, who made the move back to Stamford Bridge during the summer following two years away, sat out Saturday's 4-2 victory over Swansea City but was thrown back into the starting lineup for yesterday's 1-1 draw with Schalke 04.
Drogba missed a key chance to put the game beyond the Bundesliga side's reach in the second half, dragging his effort wide of the target before Klaas-Jan Huntelaar equalised.
"I had [chances], especially the one in the second half," the Ivorian told Chelsea TV. "It was a clear chance and I think it's unlucky.
"If I score there there's no more game. The fact that you don't score, they still believe in the equaliser and that's what happened afterwards.
On his comeback to the team, he added: "The good thing is that there is no pain in the ankle, so now I can start working and training and improve the condition. I was feeling much better in the second half. I'm like a diesel, I need time."
Chelsea are back in action on Sunday when they take on Manchester City in the Premier League.