Although the disciples are not a part of the world, they are in it (17.11), and it is their calling to remain in the world. So Jesus does not ask the Father to remove the disciples from the world, but to keep them safe from the Evil One. It is possible to translate the Evil One as an abstract noun meaning “evil.” However, most translations see here a personal reference. The Evil One is to be identified with the devil, who, in Johannine theology, is “the ruler of this world.” The Evil One is referred to again in John 2.13-14; 3.12; and 5.18,19. To indicate clearly that the Evil One is a title, it may be necessary to say “keep them safe from the one who is known as the Evil One” or “… the one who is called the Evil One” or “… whose name is the Evil One.” In some languages, one may use such an expression as “keep them safe from the one who is truly evil” or “… really evil.” The identification of the Evil One with the devil may be made specific by means of a marginal note.

Quoted with permission from Newman, Barclay M. and Nida, Eugene A. A Handbook on the Gospel of John. (UBS Handbook Series). New York: UBS, 1980. For this and other handbooks for translators see here .