CNN's Erin Hawksworth first reported the news.
Pelissero adds that Washington looked to trade the former third-round pick in March, so the timing of this move is odd. Redskins veterans are set to report to training camp Wednesday and their first practice is Thursday.
Foster, an eight-year pro, started all 16 games for Washington last season and was seventh in the league with 131 combined tackles. He also had a pair of interceptions and fumbles recovered.