The two center backs of any team (assuming a flat back 4) is the foundation of defense. Not only do the best center backs in world football show ferocious and strong defending, but also a good touch and technique going forward. The best center backs are called upon to build play from the back and thus become arguably the most important position on the pitch. I have rated the players based on current for. The 2010/2011 season until now, is the time frame, enjoy.
Nesta represents the gold standard of the 2000's first decade. Here are the current top 15.
Notable mentions: Nesta, Samuel, Chiellini, Ferdinand, Carragher, Lucio, Gallas, Mertesacker, Friedrich