"It was a difficult situation coming in with the whole Tohu thing, and I feel very remorseful,'' Williams said at the Kiwi team's camp in Sydney on Sunday.
"But I didn't want to look back in 10 years at something that I would have regretted.
"When it first came out, I said to the coach I am willing to drop out because I felt that bad.
"But he told me I had the backing of the senior players and now I just go with the coach's decision.''
Kearney admitted the situation wasn't ideal, but shrugged off criticism at handling of the issue by many including former Kiwi coach Graham Lowe.
"There were always going to be people who agreed and disagreed with the decision,'' Kearney said.
"But the most important thing is that we've made it and we have to put it behind us.
"We feel for Tohu but now we have to get on with the job.''
Speculation was rife on Thursday that Williams was returning to Super Rugby with the Chiefs next year when he was spotted signing documents while lunching with team officials and senior management from the NZRU in Sydney.
But 24 hours later, the Roosters confirmed he was staying with them for another year and Williams said the documents at the lunch were merely him making a declaration of interest in returning to rugby in 2015.
"It was making my intentions clear; the deal hasn't been done yet. I was clearing up a few things and being up front and honest with them,'' he said.
"It's how I've always been and my year here at the Roosters couldn't have gone any better.
"I know people will take it the wrong way but I can't worry about that.
"I will always have that with whatever I do, but I had to do what felt right in my heart and my gut.''
Williams said when Kearney first made contact with him on Monday - 24 hours after helping the Roosters beat Manly in the grand final - he was leaning toward going back to rugby union and didn't feel he should play the league World Cup in that case.
But the prospect of becoming the first man to win a World Cup in rugby union and league was a challenge he couldn't miss.
"To be honest, I hadn't made my mind up until 24 hours after I spoke to Mooks (Kearney),'' he said.
"That was the hardest thing. When I spoke to him, I'd just got back from not much sleep after celebrations.
"When we spoke, the body was a bit sore and we didn't really know what I was going to do and it looked like I was going to go back to rugby.
"I felt if I went back to rugby, it wouldn't be right putting my hand up for the (league) World Cup.
"But I decided I was going to stay and, for elite players, the pinnacle of what you want to do is play for your country.
"I still haven't beaten Australia or England and to play in a World Cup is going to be special.
-AAP
