The midfielder grabbed his fourth goal of the season for their draw with Sunderland.
"He's a massive player for us and we probably missed him a little bit while he's been away," Williams said.
"But he slotted right back in and was as good as he's been all season.
"Ki and Jack Cork put in good shifts and I thought Jack covered a lot of ground on his debut.
"I was a little bit disappointed with the way we played but we showed great character to come back from a goal down, especially when you're not playing as well as you want to.
"We've had a bit of a wobble after Christmas but we've got four points from the last two games and we want to kick on now."