Benitez said: "We have played around nine games a month, so we have played more games than anyone in Europe.
"But we knew that before the game (against Sparta) so I rested some players so hopefully the players we use will be fine and we can keep the energy.
"When you play two games a week in two different competitions and you rest a few players and you win they will say 'Fantastic rotation' but if you lose they say 'Why are you resting these players'.
"We will change some of them against City, that is very clear because we have to do it and that is the way if you are a top side.
"Because the club is successful that is part of the price you have to pay and we are really pleased to be paying this price."