Finau ground out a hard-fought two-under 70 to end Saturday at 13-under par overall, three strokes ahead of playing partners Rose and Masters champion Patrick Reed
WGC-HSBC Champions: Tony Finau leads defending champion Justin Rose going into Sunday's final round in Shanghai
Justin Rose will have one more day to try to catch leader Tony Finau after the American fought off a challenge from the defending champion in the third round of the WGC-HSBC Champions tournament.
Finau ground out a hard-fought two-under 70 to end Saturday at 13-under par overall, three strokes ahead of playing partners Rose and Masters champion Patrick Reed, who also each carded a 70.
Joining Reed and Rose at 10-under was American Xander Schauffele, who posted a 69.
Finau, who teed off with a three-stroke lead, is known on the tour for his upbeat approach to the game, and it came in handy after he surrendered the leaderboard to the English world No 3 Rose with two bogeys on a shaky front nine at Shanghai's Sheshan International Golf Club.
"There was no need to panic. Just play some good golf coming down the stretch and I was able to do that," Finau said.
"I feel like my attitude is like this a lot. Never too up, never too down, at least for the most part. It usually serves me well in this game."
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.
"That was my best stuff there. Any time you can have a kick-in on a hole like that when you're just trying to make a three, it's a big bonus," he said.
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 USA captain's pick in last month's crushing loss to Europe.
His only PGA win so far was the 2016 Puerto Rico Open.
But his star has risen, with 11 top-10 finishes in 2018, including at three majors, and his Ryder Cup performance. He is currently the world No 17.
"I'm looking forward to tomorrow," Finau told the European Tour's website.
"I've got a world-class field chasing after me. This is the position you want to be in and I'll be looking to close out my first tournament in this position, which is exciting for me.
"Whether it happens or not, it's an experience that you learn from and you continue to move forward.
"It was great to birdie the last three. It's always a nice way to finish no matter what position you're in.
"I didn't have a lot going my way for the first half of the day and Rosey was making his run.
"I was just really pleased I was able to finish that way and get some momentum going into tomorrow."
Rose benefitted from a final-round collapse in Shanghai last year by Dustin Johnson to come from eight strokes back for the win.
But the tables were turned on Saturday as the Englishman surrendered the crucial 54-hole advantage with a costly double-bogey on the par-3 17th after his tee shot leaked into a hazard.
He followed that with bogey on the par-5 18th with a second shot into water.
"I've got to go out tomorrow, shoot maybe something in the mid-60s and see if I can chase Tony down," Rose said.
"I'm playing well, feeling good. Just got to put that last couple holes behind me and come out a little bit angry tomorrow."
The tournament, dubbed "Asia's major", annually gathers a premier field with its winner's purse of US$1.8 million (Dh6.6m).
But some of golf's biggest names have struggled on the tricky course and in unpredictable winds.
Newly anointed world No 1 Brooks Koepka was well off the pace at one over par, while last year's goat Johnson was a further three strokes back.
Reigning Race to Dubai champion Tommy Fleetwood is five shots off the lead alongside American Andrew Putnam.
Putnam made one bogey in a 67 to sit a shot ahead of Thai Kiradech Aphibarnrat and fellow American Keegan Bradley, who both fired rounds of 70.
Jason Day was at six under, a shot clear of Thorbjorn Olesen, Patrick Cantlay and Billy Horschel.
Rory McIlroy's problems continued with a 75 and the four-time Major champion is tied for 60th on eight over.