You will hear this ad infinitum: pro football is a game of attrition.
I bring this up because the knee injury to right guard Marshal Yanda that ended his season is likely to manifest itself many, many times during the course of the season, impacting the running game and the performance of rookie quarterback Joe Flacco. The interior of the Ravens' offensive line -- center Jason Brown and guards Ben Grubbs and Yanda -- has been a strength and as a unit, the young offensive line was an area that was a building block for the future. With Yanda out, the timetable on that maturation process is set back considerably.
The options are fairly finite for replacing Yanda and none of them good. Normal right tackle Adam Terry could be moved to right guard and leave the veteran pickup Willie Anderson at right tackle. Or, the Ravens could try Chris Chester again as an offensive lineman (he had been moved to tight end after failing to impress anyone as an OL). Or, they could play rookie Oniel Cousins. The best guess is that the Ravens will opt for Terry at guard and Anderson at tackle because -- presumably, at least -- there would be less communication problems along the offensive line.
On the surface, an injury to a right guard doesn't seem to be as significant as getting a quarterback hurt, or even a cornerback or running back. But because of the domino effect that losing a key offensive lineman creates along the offensive line and, in turn, on the entire offense, such a loss can be huge.
This is a bad break for Yanda, a kid who was coming along and, on the occasions I had to deal with him, a good guy. And it's a bad break for the offense as a whole.