Patriots linebacker Brandon Spikes was absent from the team's first organized team activity, held at Gillette Stadium on Monday, a league source confirms. The reason for the absence was unclear, but as colleague Mike Reiss noted on Sunday, Spikes has not been present much at the team's facility throughout the offseason. OTA's are not mandatory, and Spikes has the right to miss out on one or any of the sessions. Nonetheless, absences are notable as the team normally has close to perfect attendance at the on-field sessions. OTA's provide an opportunity for players to work with their new teammates and coaches for the first time since the conclusion of last season, and are often used to install a substantial portion of the playbook.