Originally Posted by Kuruharan

So which is it? You are arguing both points.

The "might be expected" part implies that it was not a sure thing that even Gandalf would be able to defeat Sauron even if he mastered the Ring.

Let me do some added emphasis...



This is a statement of the unique stature of Gandalf. I don't see how it could be taken any other way.

Please, feel free to explain why Saruman could have mastered the Ring and proved a match for Sauron. However, bear in mind that you have already mentioned part of the answer to this riddle...



...and that Tolkien said elsewhere...



For a variety of reasons, Saruman was not on Sauron's level and could not be expected to successfully contend with him.

Oh, by the way, there is also another thing relevant to this topic in this little piece...



I think this sheds some light on the original question.