First in a series of positional looks courtesy of Yahoo! Sports Contributor NetworkThese days in the National Football League, there's so much emphasis placed on the performance of the quarterback that you wonder if he's the only player on the field.Someone has to run the football and someone certainly has to catch it. If the quarterback doesn't want to spend the afternoon or evening on the turf, it's safe to say someone has to block for him as well.There's also the defense getting that other team off the field, as well as the special teams doing their best to improve field position.So here's the first of many looks at the other positions on the field and their importance. A one-man show is great in tennis, bowling and handball. It doesn't work when it comes to football.First up it's the running backs. Which teams value one of the other guys in the backfield more than most? Here's a small sampling:http://sports.yahoo.com/news/nfl-running-back-driven-league-194000590.html