The 20-year-old has been named in Wales's Six Nations squad, along with four other uncapped players, after impressing with some eye-catching performances in his first season at Ospreys.
"He's an outstanding player and a great friend as well. He's definitely someone to look up to," said Walker.
"I'd like to think I have learned a thing or two. He is any winger's hero in Wales and in world rugby."
Williams retired from international rugby in 2012 after being capped by Wales 87 times and playing four times for the British and Irish Lions.
Walker has scored five tries in 13 appearances for Ospreys this season.