"It's a great challenge for him and one I'm sure he'll relish.''
While Kirwan had taken into account Williams' recent history of injuries, he said the 2-metre lock was ready to take on the responsibility of captaining the side and proving his doubters wrong.
"He's had a bad run of injuries, but I think he's ready for this because he's had a bad run and some people think he's finished. I don't believe that and neither does he.
"I think he's got a heck of a lot to offer this franchise, he's a world class lock with the ability to lead a team and I'm extremely enthusiastic and positive about this decision.''
Williams, who returned from England yesterday following the All Blacks' end of year tour, said it was an honour to captain a side he was so passionate about.
"I am a hugely passionate man when it comes to the Blues and it is a great honour to lead the team next year,'' Williams said. "It's an extremely tough job and I respect that.
"There have been many great leaders of this team before me and my job along with the team is to strengthen the strong traditions that the Blues have.''