According to Rapoport, the new deal was adjusted to advance Williams half of his cash for the 2020 season and guarantee it. Williams also passed a physical for the team.
Williams was set to make a base salary of $12.5 million in the final year of his deal.
After San Francisco traded for Williams, the expectation is that the two sides will allow the 2020 season to play out before evaluating a potential extension.
Williams, 31, is a former first-round pick of the Redskins back in 2010. He currently in the final year of his five-year, $66 million contract that includes $43.25 million guaranteed and stands to make a base salary of $12.5 million for the 2020 season.
In 2018, Williams started 13 games for the Redskins. Pro Football Focus rated Williams as the No. 21 tackle out of 80 qualifying players.