Sullivan was waived by the Seahawks on Saturday, John Boyle of the team's official site reports.
The Seahawks selected Sullivan in the seventh round of April's draft with hopes that the 6-foot-5, 245-pound wide receiver could be converted to tight end. However, the LSU product couldn't effectively make the switch, so the Seahawks opted to keep four established tight ends. If Sullivan clears waivers, expect the Seahawks to continue to develop him on the practice squad.