"If I'm totally honest, I just wanted to get on the bench for the England game to earn my 50th cap," Williams said. "Then I got injured with Cardiff, so I didn't think I'd even make it that far.
"But Colin injured his foot, and my injury healed quicker than everyone thought, and here we are. I do feel for Colin, because he was there through all the tough times and he's worked as hard as any of us."
Williams said he hadn't had time to ponder his new unofficial title as the best player in the Northern Hemisphere.
"It hasn't really sunk in yet, it's a huge honour but there are number of guys who could have picked up the award," the 29-year-old said. "I'm just lucky to be playing in a team performing so well. I think any No.7 would look good playing in this Wales team at the moment.
"Our success hasn't been a magic formula, it all comes down to hard work and we don't want this success to be a one off, we want to win a few more things in the next couple of years."
Williams is a red hot favourite for one of the backrow spots on the British and Irish Lions tour to New Zealand, and he won't be short of Welsh company.
"Most of the Welsh side have put their hands up for the Lions tour, and it's not just the starting lineup against Ireland," he said. "We've got injured players who are world-class, such as Gareth Thomas, Gareth Cooper, Colin Charvis and Dafydd Jones, who must all be in with a great chance."
Williams said Wales's away form was the key to their first Grand Slam in twenty-seven years.
"Everyone talks about Gavin Henson's kick against England or our comeback against France, but for me, the highlights were our performances in Italy and Scotland. We went over there and dominated both games, which we haven't been able to do in the past, and that's when I started thinking we were a very good team."