Mo missed valuable time with the wrist injury last year...both on the field and in the weight room. This year his arms, etc...look noticeably bigger. And as coult44 mentioned, his battles with Dez will no doubt only make him better. Dez is a beast for ANY CB to handle one-on-one.
As far as Newman...he was an elite athlete when he came out of K-State. He was the Big 12 Conference 100 meter outdoor champion & 60 meter indoor champ. So simply being an elite athlete doesn't spell success throughout a career. It certainly helps, but Troy Vincent wasn't an elite athlete. Also, though Newman's play declined in Dallas over his last few seasons, he wasn't too bad for the Bengals last year.
Both Newman and Claiborne won the Thorpe award.
This was Mike Mayock's take on Claiborne on NFL.com: "One of the main reasons I think the Dallas Cowboys haven't been to a Super Bowl in some time is because of their secondary. Morris Claiborne is a special corner. He's got the best ball skills of any corner coming out in the last several years. This is a rare athlete."
In terms of being a 'rare athlete'...I don't think that was directed at speed, etc...as his best 40 time was 4.47. Mo has a very good combination of size, arm length, solid leaping ability, very good hip swivel for his length, and did in fact display uncanny ball skills coming out...which I expect to start seeing more of as his confidence continues to grow.