First, they've placed OL Tyronne Green on the Injured Reserve. Green is a veteran guard that the Patriots picked up in the off-season, hoping to replicate their luck with OG Donald Thomas. Green's injury is still unknown, but the Patriots are keeping him around for the off-season. Green played with the Chargers and has 28 starts under his belt.
Second, they've released veteran OL Kevin Haslam. Formerly of Rutgers, Haslam was one of the numerous acquisitions over the off-season. Haslam provided some tackle depth, but was unable to stay on the field. He started three games at left tackle for the Chargers last season.
This leaves three open roster spots for the Patriots. Look for more offensive line talent to join the roster, as well as either someone in the secondary, defensive line, or wide receiver corps.
Beyond the top 7 linemen on the roster (Nate Solder, Logan Mankins, Ryan Wendell, Dan Connolly, Sebastian Vollmer, Marcus Cannon, and Will Svitek), there are only two non-rookies left competing on the line. There's second year, and still-injured, T/G Markus Zusevics and there's former college defensive lineman IL Luke Patterson, who has spent his last two seasons learning the offensive line of the ball.
Everyone else competing is a rookie. Perhaps Cannon and Connolly are ready to take the field. Regardless, look for the Patriots to bring in a veteran for another run through.