I chose Lee, 12-2 with Cleveland, a team that has really played poorly. The 2.31 ERA is not as low as Duke's, but still very good.
Dice-K... Sorry but I can't see him as a consideration. How he maintains that low of an ERA with the way he walks guys is unbeknowst to me. He's just darn lucky. Also he would be far more helpful to his team if he would last more than 5 or 6 innings per start, but you can't leave a guy in for the 6th and 7th inning when he has already thrown 120 pitches.
Rivera... The 4 votes for him had to be Yankee homer picks. Just over half as many saves as K-Rod. As far as his ERA, it's impressive, no doubt. But Duke has pitched 66 more innings and his ERA is only .80 runs higher. Rivera won't pitch 108 innings this season, but I'll almost guarantee his ERA will be higher than 1.06 by season's end.