Saying Barnwell is voting Martin in on reputation is laughable. The guy studies film weekly.
Here's what he says on Martin.
Offensive linemen sometimes receive accolades well past their peak, if only because there's no common measure we can easily rely upon to judge their performance. Ask around the league and talk to people who are watching linemen each week, however, and you'll hear as many raves about the 33-year-old Martin now as you did five years ago. Enough of the physical tools that allowed him to play left tackle in a pinch are still around, and he has seen everything opposing defenders can throw at him by now.
Some college tackles who move inside at the NFL level can struggle with their strength or ability to hold off bigger defenders; first-round pick Peter Skoronski is dealing with that right now for Tennessee. Martin was one of the conversions who adapted immediately. He ranks fourth in run block win rate among guards this season. It still seems impossible that the Cowboys debated between picking the future Hall of Famer or quarterback Johnny Manziel in the first round of the 2014 draft.