Dustin Johnson will face rising starJon Rahm in theWGC-Dell Technologies Match Play final after the world number one recovered from a wobble to beatHideto Tanihara one up.
Johnson looked set to be cruising in his semi-final against theMatch Play debutant when he was three up through seven holes at Austin Country Club, but the surprise package from Japan mounted a stirring fightback.
Four birdies in seven holes resulted in the world number 60 moving back to all square after 14 and Johnson might have wondered if it was not his day when he spurned chances to move back in front.
TheU.S. Open champion, eyeing a third consecutive tournament win, had not been required to play the par-three 17th all week,but the top seed took the upper hand with a birdie at the penultimate hole after a magnificent tee shot.
Tanihara could only make par, but had a great chance to take a gripping contest to a play-off when Johnson's approach shot found the rough, with the 54th seedon the green.
ButTanihara was unable to sink his birdie putt to prolong the match, enablingJohnson to recoverbysalvagingpar and setting up an eagerly-anticipatedshowdown with Rahm.
SpaniardRahm had long since sealed his place in the final after endingBill Haas' challenge with a three and two victory.
The impressive Rahm has gone from strength to strength this week and continued his upward momentum despitefalling behind for the first time since Wednesdaywhen Haas rolled in an expertly judged birdie putt from the edge of the green at the third.
Rahm, seeded 21, hit back to lead following back-to-back gains at five and six before surging away from the American by winning the 13th, 15th and 16th holes courtesy of further birdies from the former amateur world number one.