From ESPN
Minor makeover for offensive line
The Texans did a little tinkering with their starting offensive line on May 24, using second-year player Seth Wand at left tackle and moving Chester Pitts one spot to left guard. Coach Dom Capers stressed the move was experimental. "Nothing is etched in stone," he said as the second week of the four-week offseason coaching session began. Wand, taken in third round a year ago out of Northwest Missouri State, was considered a project as a rookie but excited coaches with his potential and his massive 6-foot-7, 327-pound frame. Later in the season he was often employed as a second tight end in run formations. Pitts has been the left tackle for every snap in the Texans' two-year history.
This was the plan from the begining. However it was supposed to Bos at Tackle and Pitts at Guard. When Bos left well Pitts had to hold down the fort until Wand is ready.