As long as your knife is clean and dry when you put it in the saya you should be fine. But I generally prefer cardboard for work knives. Cardboard is free and takes up less space in a knife roll and if they get messed up I just make new ones.
Agree with above...knives should always be diligently cleaned and dried before they are put away, regardless of protective storage method. Aside from gunk, I don't want my blades to rust. I don't take my sayas to work. I pick the knives I am going to bring that day, leave the saya on my display rack, then use felt lined knife guards, or leather sheaths to take them to and from work.