Who is the best defensive player in the NFL?

It's all according to position but if I had to choose 1 and 1 only, it would be Revis. To completely shut out your opponents #1 receiver week in and week out allows the defensive schemes to alter and surprise opposing offenses. Have you seen the stats for the last couple of years of star/stud receivers "stranded on Revis Island?" It's amazing. Polamalu certainly has a case also.