Webb Simpson produced a stunning End to snatch a dramatic victory.
Simpson birdied his final two holes to post a 69 in TPC Scottsdale and finish under after missing a putt for victory on the last 37, alongside Finau, who carded a final-round 70.
In which Simpson wrapped in an 12-foot birdie to assert a sixth PGA Tour title and first the pair returned to get a play-off to the 18th.
Justin Thomas birdied four of his last six holes to place a round-of-the-day 65 and snatch a share of place with Nate Lashley and Bubba Watson, while after finishing the week at tied-ninth Jon Rahm missed the chance to become world # 1.
After rolling into a only to overlook the green off the tee and place a bogey from the fringe simpson began the day a shot but pulled flat.
Finau fell behind despite holing a 25-footer to save par in the tenth, where Simpson submitted a four-foot birdie to go into the lead and created a bogey in the eighth.
The lead changed hands back after Finau followed a birdie at the 12th by holing a different from the distance at the par-five second, remain within one and with Simpson switching to save par.
Finau missed a birdie attempt in the 15th but saw his guide doubled when Simpson left bogey after discovering water before the group exchanged two-putt pars in the 16th.
Simpson cut the lead to one later forcing the 17th green before draining an 18-footer in the last to take the contest to holes and two-putting from 50 feet for birdie.
Finau enabling Simpson to steal victory by holing his attempt by the side of this green and missed a 15-foot birdie effort, found the bunker off the tee at the first hole.