Most Overrated: Jay Ratliff
Give Ratliff credit, for several years he was truly an elite nose tackle despite being extremely under-sized for the position. In a 3-4 defense, the NT is meant to take up space and is usually 330 pounds or more.
Ratliff was able to not only play the position hovering around 300 pounds, but also excell as a pass rusher. However, over the last three years, whether from wear and tear of the position or just age, Ratliff has been diminishing in skill despite still being considered an elite player at his position.
His sack totals have gone from 7.5 and 6 in '08 and '09 to 3.5, 2 and a grand total of zero last year. Despite this, he was named to the Pro Bowl in 2010 and 2011.
With the Cowboys switching to a 4-3 defense this year Ratliff moves to a position where his size and athleticism are better suited he may return to true Pro Bowl form, but his play over the last few years make him the most overrated player on the Cowboys' roster.
Most Underrated: Jason Hatcher
Another defensive lineman, Hatcher is far from a household name, but his play over the last few years has proven that he is one of the best 3-4 ends in the game. Throughout his career, and especially over the last two years as a starter, Hatcher has providing a consistent pass rush from a position that normally does little more than take up space.
In 2011, despite only starting 10 games, Hatcher managed 4.5 sacks, following that up with another four-sack game. That may not seem like much compared to JJ Watt, who also plays end in the 3-4 but it's more of a testament to how uniquely gifted Watt is than a slight on Hatcher's performance.
You'd be hard pressed to find a 3-4 end better than Hatcher outside of Watt and maybe Justin Smith, and yet he is only known amongst Cowboys fans and NFL purists. This is what makes him the most underrated Cowboy on the team.