Williams, 24, had previously played for Ipswich Town on loan in December 2023. He has been working hard to regain his fitness and has been given a chance to impress Hull City's new head coach, Sergej Jakirovic, who is looking for a left-back to join the team.
Williams took to social media to share his messages with fans, including one of inspiration as he wore the City kit during the match: "20 long hard months, it pays off. Back in love, back with fire, back with determination."
In another post, he asked fans to give him time to work back to 100% ahead of the new season: "Just give me time to keep working to 100% #Comebackispersonal. Back to life, back to reality."
He also addressed fans who doubted him after his fall from United to the Championship: "Dear haters, I have so much more for you to be mad at, Just be patient. For the people who doubted me."
Williams came on as a trialist for Hull City after 77 minutes, as the team showed an impressive performance against Sunderland. He may join the team to help them avoid relegation next season.