Slater and the Thrashers were scheduled for a salary arbitration hearing on Aug. 2. Slater was a restricted free agent.
The 24-year-old had five goals and 14 assists in 74 games last season with Atlanta.
He has 15 goals and 24 assists in 145 career NHL games, all with the Thrashers.
The six-foot, 190-pounder was drafted by the Thrashers in the first round, 30th overall, of the 2002 NHL entry draft.