Haslam, 26, is a veteran of three NFL seasons with the Jacksonville Jaguars (2010-11) and San Diego Chargers (2012). The 6-foot-5, 304-pounder, originally entered the NFL as a rookie free agent with Jacksonville out of Rutgers in 2010. He has played in 10 NFL games with three starts.
Haslam played in five games as a rookie for the Jaguars in 2010 before being placed on injured reserve and then missed the entire 2011 season due to an injury. Haslam was released by Jacksonville after the 2011 season and was signed by Oakland in the offseason. After being released by Oakland at the end of training camp, Haslam was signed to the San Diego practice squad. He was signed to the 53-man roster in Week 11 of last season and played in five games with three starts at left tackle.
Mattes, 23, was signed by the Patriots as a rookie free agent on May 13 out of North Carolina State. The 6-foot-6, 313-pounder, was a four-year starter at both guard and tackle.