Day, who will replace Jordan Spieth at the top of the world rankings today by virtue of his performance at Austin Country Club, won a hard-fought contest by one hole to set up a final with former Open champion Louis Oosthuizen, who defeated Rafael Cabrera-Bello 4&3.
McIlroy has never successfully defended a title in his professional career and was famously prevented from even attempting to do so in last year’s Open and WGC-Bridgestone Invitational, after suffering a serious ankle injury while playing football.
The world number three had made no secret of wanting a win under his belt before attempting to join Gene Sarazen, Ben Hogan, Gary Player, Jack Nicklaus, and Tiger Woods in completing the career grand slam at the Masters.
And the 26-year-old felt his excellent match play record gave him a great chance of following the likes of Day, Spieth, Bubba Watson, Adam Scott, and Charl Schwartzel into the winner’s circle this year in his final competitive outing before heading to Augusta. However, after twice edging ahead on the front nine with birdies on the sixth and eighth, his semi-final with Day turned in four holes at the start of the back nine.
Day got back on level terms with a birdie on the 10th and then crucially saved par from left of the green on the 11th before McIlroy missed his birdie attempt from five feet.
The US PGA champion then birdied the next two holes — his approach to the par-five 12th narrowly clearing the water surrounding the green — as McIlroy duffed his chip to the 13th to fall two behind for the first time.
McIlroy, who would have equalled Tiger Woods’s record of 13 matches without defeat in the event with a win, did reduce his deficit with a birdie on the 14th, but after both players birdied the 16th, Day produced a brilliant par save on the last to seal victory.
A disappointed McIlroy said: “I thought it was a good quality match. If I have to look back on it, there were a couple of opportunities around the third and fourth where I didn’t convert and not birdieing 12 or 13 was the real downfall.”
On the positive front, McIlroy felt the week had been “very valuable” preparation for the Masters, adding: “I was saying coming into this week that no matter if I play three, six or seven rounds, playing match play and feeling like you are in contention every time you step on the first tee is a great feeling, and something you can’t replicate in practice.
“The week has been very positive overall; I wish I would have been able to get one more win under my belt, but I am very happy with my game going into Augusta.”
In the other semi-final, Oosthuizen threatened to let slip an early three-hole lead after careless bogeys on the eighth and ninth, but birdied the next and then saw Cabrera-Bello miss good chances on 12 and 13 to get back into the match.
And Cabrera-Bello, who qualified for his Masters debut by reaching the quarter-finals, then bogeyed the next two holes to give Oosthuizen a comfortable success.