Typically, during the fourth game of the preseason, a team's most key contributors sit for the majority, if not the entire game to be cautious about their health entering the season. After losing out to Derek Newton for the starting right tackle spot, Rashad Butler became a backup, but was still very useful to the team as a swing tackle.
When the tackle torn his triceps and was lost for the season, Tim from Battle Red Blog talked about the importance of the injury:
Although Butler lost the fight to start at right tackle to Derek Newton, he was invaluable as a backup swing tackle, thanks to his experience on both sides. I'm not quite sure where the Texans go from here. Brandon Brooks might be able to back Newton up at RT (I stress "might), but there's no one on the current roster who would seem to be a viable backup for Duane Brown on Matt Schaub's blind side. I'm not really buying Andrew Gardner as a replacement for Rashad Butler.
As Tim notes, the starting lineup for the Texans will not change but the impact on the depth on the offensive line is huge and could force the team to start fishing for a new tackle on the waiver wire.