The 22-year-old has played on the outside throughout his college and NFL career to date, but is making the move inside this year after impressing in the role briefly last season.
"To his credit, he's really working at it," Williams told reporters. "He's coming along faster than I think that he even thought he would because he hadn't been inside.
"I think he's embracing it and liking the position in terms of what we allow him to do and the plays that he can make. I feel good about Josh being inside."
The Vikings begin their regular season campaign against the Detroit Lions on September 8.