If you have contamination on your disc brake rotors you will have a bad time. It's a common reason for squealing disc brakes and it can also cause stopping problems. Chain degreasers are not always designed to leave the metal surface completely free of any residue. The seals on disc brake calipers are also not designed with solvents in mind. To make sure you don't have an issue you are going to want to make sure to keep whatever cleaner you use off any part of the disc brake system.