Williams had a hand in each of his team's two first-half tries, which proved pivotal in the end when the Blues launched a strong second-half comeback.
Returning to the Chiefs after spending the last two seasons playing rugby league in Australia, Williams helped set up tries for James Lowe and Bryce Heem.
"It was a very tough game," said Chief skipper Matt Symons. "It was good to get away with the win but there's still plenty of things to work on."
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The Chiefs, who won back to back Super Rugby titles in 2012 and 2013, opened up a 20-6 lead in the first half before the Blues came back strongly in the second term.
Although they did not score a try, the Auckland-based Blues kept chipping away the lead by kicking six penalties, all from Ihaia West.
"There were a lot of positives we can take out of this," Blues captain Jerome Kaino sad. "The forwards went bout their work well and the backs did some good things too."
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