The Blues won the first leg against Juventus 1-0 at Stamford Bridge on Wednesday.
The Ivory Coast striker said in the Daily Mirror: “In the second half it was more difficult for me, and in the one-on-ones I didn’t really have the legs to dribble.
“I need to work on that but the best place for it is on the pitch because we have games every three days, which means training will be limited.
“The manager said after the game that we’re not in tip-top condition and we feel it too.
“We need to put in a bit more effort to help each other. But you could see it was difficult for us to carry ourselves from our half to the opponents’ half in the second period.
“From around 70 minutes we get heavy legged. You will have to ask a fitness coach why that is and I’m not one. But we know we have to improve.”