The news was first reported by NFL Network.
Williams has two years left on his contract, but sources told ESPN's John Keim that the Redskins are not inclined to extend him because he'd be 33 at the time his deal expires and is oft-injured. The Redskins also know that if they extend Williams they'd then have to do a new deal for linebacker Ryan Kerrigan. He, too, has two years left on his deal.
The Redskins could guarantee more money in the last year of Williams' deal; his $12.5 million base salary in 2020 is not guaranteed. Multiple sources told Keim that the Redskins are not at a point where they will consider trading him. There's still a belief in the organization that they will resolve his issues.
With Penn coming to Washington, the Redskins can move Ereck Flowers to left guard, the position they signed him to play. They also have second-year Geron Christian to play left tackle. But Christian, a third-round pick in 2018, only played in two games before tearing his MCL. He could not practice during the spring as he recovered from surgery. The Redskins signed another veteran, Corey Robinson, last week.
Penn, a longtime left tackle, moved to right tackle last season after the Raiders selected left tackle Kolton Miller in the first round of the 2018 draft. Penn played only four games, however, as he was placed on injured reserve in October with a groin injury.
Penn was selected to two Pro Bowls during his time in Oakland.
He has started 174 of the 178 games he has played in his 12-season career, including seven seasons with the Tampa Bay Buccaneers.