ESPN's Adam Schefter added Williams is "expected" to restructure the final year of his contract with the 49ers.
Adam Schefter @AdamSchefter
Here’s what helped set into motion the Trent Williams’ trade: six-time Pro Bowl and All-Decade OT Joe Staley is expected to retire due to health concerns, per league sources. The 35-year-old Staley wanted to inform the 49ers in a timely way to help find a replacement. They have.
The move ends a tumultuous, drawn-out ending to Williams' time in Washington.
Williams, 31, did not play any games for the Skins last season after demanding a trade on June 5, 2019.
Jason La Canfora of CBS Sports reported the news, citing the player's alleged disagreement with the team regarding its handling of a medical concern:
Jason La Canfora @JasonLaCanfora
Trent Williams issues with Skins are not financial at all according to numerous sources with knowledge of the situation. He's told teammates he has demanded a trade or his release from the club due to their handling of his recent medical situation. Has vowed not to play for them
One day earlier, Ian Rapoport of the NFL Network mentioned Williams' desire for a new contract:
He then followed up with more details about the aforementioned medical concern, citing his reported issues with the team's speed and handling of a discovered growth on his scalp:
Grant Paulsen of 106.7 The Fan backed up La Canfora and Rapoport's claims about Williams' unhappiness with the team:
Skins right tackle Morgan Moses defended his teammate, per John Keim of ESPN.com:
Williams never reported to camp and sat the beginning of the regular season, but he showed up to team headquarters in October.
However, he soon left the team and said the "bridge has been burned" between him and the franchise, per Mike Jones of USA Today.
But the Skins cleaned house after the season, firing team president Bruce Allen and replacing interim head coach Bill Callahan with Carolina Panthers head coach Ron Rivera.
There were signs of optimism Williams could return, with NFL Network's Mike Garafolo reporting that the tackle was either seeking a trade or a new deal to stay in D.C.
A new deal never came to fruition, though.
Letting Williams go is a huge loss for Washington and a big gain for San Francisco. Henry Buggy of Pro Football Focus explained why:
"Over the last three regular seasons (2016-2018), Williams has graded out as the NFL's third-best left tackle (89.1). He trails only David Bakhtiari and Joe Staley over that span, beating out notable players like Andrew Whitworth and divisional rival Tyron Smith.
"In 2016, the former Sooner posted the fifth-highest offensive tackle grade (92.7) in the PFF era (2006–present), and only Jonathan Ogden, Tyron Smith and Joe Thomas (twice) have recorded higher overall grades at the tackle position."
Per Over The Cap, Williams has one year left on a deal that will bring him $12.5 million in base salary and $2 million in prorated bonuses.
Without Williams, the Skins' offensive line struggled, ranking second last in the NFL in adjusted sack rate allowed, per Football Outsiders.
They will now embark on a new era without a staple of their offensive line.