The Foxes host the struggling title holders in Sunday's early kickoff.
“Everybody knows, when you look at the team and how they played (against Everton), I know the quality of that squad and manager so I am focusing on that and the quality we will face,” Van Nistelrooy said.
“We have to prepare for a great performance in our side. Being where we are we need to be spot on in all parts of football to get a result.
“For us all the games we are playing are massive. We know a certain amount of points are necessary and every second of every game is important.
“It is something which needs constant improvement and pressure to perform and get results. It is from game to game, we evaluate the game and make a gameplan to get a result against City.”
The Foxes could have Jamie Vardy back on Sunday after the veteran striker missed the Boxing Day defeat at Liverpool.
“Jamie had a small injury, a couple of knocks over the last week,” Van Nistelrooy said.
“He wasn’t totally fit at Liverpool so we gave him some time to recover. Hopefully he can make it for Sunday. He has a good chance.”