[Keeper of Dol Guldur]

A thought that myself, as I listened to the Silm on CD, rivalry rather than friendship. But not a bloodlust rivalry or anything like that. Though it is speculation, we know for a fact that Olorin and Radagast hung out with the elves that accompanied their mentor Valar, so it only seemed likely that this could happen with others. Maybe even, long before Sauron was coerced to the dark side, he and Saruman where buddies or rivals, we'll never know, but makes a lot of sense.