[FingolfintheBold]

Another thing: Saruman and Sauron distrusted
each other to the core. Sauron feared what Saruman could do if he aquired the Ring and learned to master it, hence His speed in going to retrieve it. And Saruman knew well the history of Sauron and all His treachery, and wouldnt have trusted Sauron as far as he could throw him, as the saying goes.

But for all the hatred and fear bettween them, Saruman also recognized Sauron's great power, and tried to emulate it. In Gandalf's words, he made a slave's flattery, a cheap model of the greatness of Sauron, for that was the power Saruman himself wanted above all to posess.

I cannot see Saruman, even in his pride, being foolish enough to face Sauron in open war. He would have bidded his time, climbed up the ranks, gradually gain loyalty and then try to usurpe Sauron's thrown, though all attempts would ultimatley be folly if Sauron held the ring.