Two strokes behind Rose on the back nine, Finau closed strong with birdies on the last three holes, highlighted by what he called a "perfect" iron off the tee on the 212-yard par-3 17th that set up a kick-in for birdie.
He had a pair of birdies on the par 5s, laid up on the reachable par-4 16th and made birdie, and wound up with a 5-under 67. He was stunned when his second shot in the par-5 18th spun off the front of the green and into the water, forcing him to scramble for par at the turn instead of an easy birdie or better.
If Patrick Reed felt any concern after stirring Ryder Cup controversy, he showed no trace of it on Thursday in posting a superb eight-under-par 64 for the opening-round lead at the WGC-HSBC Champions. Americans now have won 41 of the 69 events since the World Golf Championships series began in 1999.
Hsu had a two-round total of 9-under 135 on the Ta Shee Golf and Country Club, one ahead of first-round leader Jodi Ewart Shadoff, who shot 71 Friday.
Dustin Johnson faded after a quick start and shot 73.
He just missed the birdie putt. He was 14 shots behind. He had 16 pars, one bogey and one birdie for a 72.More news: Politically, The GOP Tax Cut Has Been A Huge Bomb
Finau, of Samoan and Tongan descent, is the first player of that ancestry on the PGA Tour and the first Polynesian to play in the Ryder Cup, where he provided a rare bright spot as a United States of America captain's pick in last month's crushing loss to Europe.
"The issue's obviously with Jordan not wanting to play with me", he told the New York Times after the US were thrashed by Europe in Paris.
Rose, who came from eight shots back in the final round past year to lift the trophy, was feeling good after not dropping a shot all day on the way to a five-under 67.
But the real collapse came from Rose, who had led since a short birdie on the seventh hole and appeared to be in complete control of his game. "So I was able to just hang in there and make a few birdies at the end, which is nice".
If Xiong, who turns 20 on November 9, triumphs Sunday, he would become only the second teenager to win on the PGA Tour since 1931. His score got worse each day, but he'd done enough in the first two days to give himself a great chance at his first non-opposite field event win.
Rose benefitted from a final-round collapse in Shanghai previous year by Dustin Johnson to come from eight strokes back for the win. "But there's a long ways to go".