The Old Lady lost 1-0 at Stamford Bridge following a first half goal by Didier Drogba.
Ranieri told Sky Italia: “We did not start well. In the first 15 minutes we had problems in playing our game.
“But my guys are confident (for the second leg), we will have to play a perfect match. I would have preferred to play less well and score at least a goal today.
“It will be a difficult match, but my guys are convinced we can recover, and I’m confident and I believe.
“Now we will have to see how we feel in two weeks. We will have to run more than them, putting them under pressure.”
