Rory McIlroy finally tasted defeat in the WGC-Dell Match Play, as Jason Day battled his way through to a final against Louis Oosthuizen.
Jason Day moved to within one win of celebrating his return to the top of the world rankings with victory at the WGC-Dell Match Play, overcoming defending champion Rory McIlroy in an absorbing semi-final on Sunday.
By reaching the last four the previous evening, Day ensured he will reclaim the number-one spot from Jordan Spieth on Monday when the new rankings are released.
And the Australian was able to get one over his other main rival as he ended world number three McIlroy's long unbeaten run at this tournament with a 1up win, setting up a final meeting with Louis Oosthuizen.
McIlroy played the better golf over the front nine of Sunday's first semi-final at Austin Country Club, but was only one hole to the good at the turn and then lost the initiative in a key period of play.
After winning the 10th, Day produced a superb up-and-down to earn an unlikely half at the par-three 11th as McIlroy missed a short birdie putt.
The US PGA champion then won the 12th and 13th to move two up with five to play, ultimately leaving his opponent with too much to do.
McIlroy dug in impressively, winning the 14th and almost pulling level when a birdie attempt at the penultimate hole slipped agonisingly past the target.
Both men then made a mess of the 18th, but Day rolled in a clutch putt from around 12 feet – with McIlroy facing a shorter par-saver – to seal victory in style.
Oosthuizen overcame a brief wobble to beat Spain's Rafael Cabrera-Bello 4 and 3 in the other semi-final.
After easing into a three-hole lead through seven, Oosthuizen saw his lead cut to one when he was punished for catching approach shots heavy at the eighth and ninth.
However, a birdie at 10 got the South African, who beat Spieth at the last-16 stage, back on track and Cabrera-Bello was unable to recapture his form from earlier in the week as his tournament came to an end at the 15th.