Re: Texans have officially re-signed T Ryan Harris
From what I understand, a lot of teams employ the Under front, especially in nickel (ie. passing situations.)
It provides one-on-one matchup on the weak side on the LT and the LG.
In this situation, the LG will face a 3-tech defensive linemen (or the Under Tackle), usually a quicker guy that can penetrate.
The LG also needs to pick up a possible stunt by the Weak side DE (usually the best pass rusher) or a possible blitz by a LB.
Therefore, I would say the LG needs to be a good pass protector.
Experience also plays a factor here.