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Williams, a two-time Rugby World Cup winner, is out of contract following the global showpiece in Japan later this year and turns 34 in August.
He had previously hinted that he might look to return to rugby league or seek out a coaching career at the end of his contract and said on Tuesday at training with the Blues that it could be his last with his hometown side.
"It could be, bro, it could be," he told the New Zealand Herald when asked if it could be his final season at the Blues.
"If I did finish at the end of the year, as long as I competed every day and put my best foot forward as a person and a player I'll be happy."
Williams is a certainty for Steve Hansen's Rugby World Cup squad, pending any injuries, something he recognised had blighted him, over the last two seasons.
Williams tore his Achilles while playing rugby sevens at the Rio Olympics in 2016 and has battled with wrist, knee, hand and shoulder injuries since.
The inside centre, however, said that he was now back at full fitness and was hoping to get through 2019 injury free.
"For the last two years I've been so methodical with my planning and preparation," he said. "Every off-season: 'A, B, C, D and I'm going to get to E'.
"It starts here with the Blues. I want us to have a successful year. I want the boys to succeed."
Williams added he would be available for selection for the Blues for their opening Super Rugby match with the Canterbury Crusaders at Eden Park on Feb. 16.
He was also relishing the competition for places at the Blues, with fellow World Cup-winning centre Ma'a Nonu back in New Zealand rugby with the Auckland-based franchise after three seasons in France following the 2015 tournament victory.
Both prefer to play in the number 12 jersey, but Williams said they were quite comfortable in the same midfield if required.
"We've always had a good friendship. It's no secret that we've always competed for the same position, we're out here competing as you can see but we're laughing and bringing out the best in each other as well," he added.
"I feel like some of the best games we've played for the All Blacks have been together. I don't think that will be an issue."