I'm really trying to understand why any O-line has to "work together" to be good. I hear it year after year but I always see the top lines in the league are the ones with the best players. Talent is paramount. Right?
Absolutely. As long as the defense promises to rush in a straight line and not use any stunts.
Cute, but that doesn't change anything. Skilled O-linemen can handle pass-rush moves and stunts. Explain to me what playing together in the pre-season does for them.
He's right though. NFL defenses are complex in their blitz schemes. Lineman need to have a feel for how the guy next to them reacts when men come from unanticipated directions. It isn't about technique at that point, it's about immediately adjusting on the fly as a cohesive unit. Those types of instantaneous adjustments can't be simply coached...the group needs to play together.Ever watch a play where a LB streaks through the middle of the line untouched to plaster the QB? Often with at least one O-lineman completely unengaged? More often then not...one of the lineman is a backup or new at his spot on that line when that happens.
29 plays of 30, it won't matter, and talent/training will suffice, but NFL games can turn on just 1 or 2 plays. A single sack like I just descibed can kill a drive, and cost a game. A sack easily avoided by a line who has worked TOGETHER for several weeks.
if for no other reason than because this team could use a little positivity these days. C'mon, let's be honest. How many people were ecstatic when the Eagles took Justice in the 2nd round? 
The blocking assignments don't change whether the 1st string or 2nd string is in there. If the guy knows his assignment, and is physically capable of handling it, chemistry doesn't mean ####. Some NFL offensive lines and have back ups come in and not miss a beat. others fall apart. It all comes down to how talented and prepared the replacement is. I think the Eagles have an above average chance of having their replacements succeed since Andy reid should have them well prepared, and they are getting plenty of reps since the injuries happened early. It's no gauruntee they'll do well but they have a better chance than most teams who have lineman get hurt IMO.
