The Bundesliga side face PSV in the Europa League on Thursday.
“On the pitch it is no problem for me to fade out all those memories for 90 minutes. I am professional enough. It will be a very special day for me though,” van Nistelrooy said to uefa.com.
“PSV are my club. I had three gorgeous years there and this will be the first match I have played against them since leaving. I am very excited.
“Week on week I am getting stronger. I think I am fit enough to play 60 minutes and I hope to get as long as possible.
“The most important thing is the team performance. We want to be in a good position for the game in Eindhoven on February 25 because PSV are very strong at home.”