Day – who will play Victor Dubuisson who defeated Ernie Els, 1 up, in the week’s final bout – built a 3-up lead through 11 holes but appeared to lose momentum when he lost No. 12 with a bogey and failed to birdie the par-5 13th hole.
But the Australian birdied the driveable 15th hole and Fowler three putted from 7 feet at the 16th hole to end the match.
“It was a tough day,” said Day, who lost to eventual champion Matt Kuchar in last year’s semifinal. “Rickie is playing great golf and I knew if I gave him a little inch he would take advantage.”
Dubuisson fell behind early in his match against Els, but birdied Nos. 8, 9, 11, 13 and 15 to take a 1-up lead to the last and scrambled from behind the 18th green to close out the South African.
“This morning I was not feeling comfortable,” said Dubuisson, who is playing his first WGC. “I didn’t sleep very well and when I arrived at the golf course, I don’t know why I realized I was in the semifinal of the World Golf Champions against Ernie Els. I’m a big fan of Ernie.”