Can my opponent discard a duplicate to cancel watchful servant's ability?

Example:

I am attacking my opponent in a mil challenge with a enemy informer. He has Ser Arys standing with a dupe. He declares him as the defender. I use watchful servant's ability to remove him from challenge. He removes dupe to cancel.

Thanks for any clarification help.

No. Duplicates only save from effects that would make cards leave play.

Ok, that's what I thought as well. Thanks Khudzlin.