Foster's injury came on the first day of the team's OTA off-season workouts. The former San Francisco 49ers defender laid on the ground, smacking the turf as members of the team's medical staff assessed the left leg injury. Foster was brought to tears during the incident. He was then taken off of the field on a cart.
The No. 31 overall pick in the 2017 NFL Draft had 72 tackles, seven tackles for a loss and a pass defensed in 10 games during his rookie campaign. He had 29 tackles, three tackles for a loss and a pass defensed in six starts last season for the 49ers.
San Francisco waived foster in November before he was claimed by Washington. Foster, 25, was suspended for two games in 2018 for violating the NFL's policy on personal conduct and substance abuse.
Foster was fined in April following a November arrest relating to allegations of domestic violence. Florida prosecutors dismissed a misdemeanor domestic violence battery charge against Foster in January.
The Redskins continue OTAs on Tuesday before returning on Thursday for the voluntary workouts. Washington begins mandatory minicamp on June 4.