"Our attacking play was maybe a little too slow," the City boss said after the 1-0 defeat at Stamford Bidge.
"We're an attack-minded team, but we didn't have that sharpness that you need when you come up against one of the top sides.
"I just think we looked a bit leggy today. The difference in preparation time told in the end.
"The fact that we were missing key personnel as well didn't allow us to have that spark or dynamic play we've had in recent weeks.
"We switched off briefly for the goal we conceded. At that point, Chelsea were quite comfortable to protect that lead, and we didn't ask enough questions of them because we lacked that spark."