Dustin Johnson had reason to be rattled. As he walked off the 12th green Saturday afternoon, the match referee said five words that Johnson heard for the first time all week in the Dell Technologies Match Play.
"The match is all square."
Until then, Johnson had led after each of the 71 holes he had played at Austin Country Club.
He wasted little time responding to a rare challenge. Johnson birdied three of the next four holes for a 3-and-2 victory over Alex Noren to advance to the semifinals and stay on track for a potential showdown between No. 1 in the world and Jon Rahm, golf's brightest young star.
"I wasn't frustrated that I was all square. I was frustrated that I kind of gave 10 and 11 away," Johnson said. "Came back strong after losing three holes in a row."
Rahm was so dominant he played only 27 holes in two matches Saturday. He hasn't had a match go longer than 14 holes since Thursday. And the 22-year-old rookie from Spain still hasn't played the 18th hole since a practice round Tuesday.
"The golf I've played the last three matches really has been very impressive, even to myself," he said. "And it seemed to get better as I played, which is something that doesn't happen often."
Rahm lost only one of the 27 holes he played in his 6-and-4 victory over Charles Howell III and his 7-and-5 victory over Soren Kjeldsen in the quarterfinals.
Rahm faces a semifinal match Sunday morning against Bill Haas, who ended Phil Mickelson's hopes with a 2-and-1 victory. Mickelson had advanced to the quarterfinals for the first time in 13 years with a victory against Marc Leishman.
Mickelson never trailed in any match until he fell behind on the first hole to Haas, and he had never led when the match ended on the 17th hole.
"I struggled making the putts that I have been making all week," Mickelson said. "That seemed to me to be the difference."
Johnson, going after a third straight PGA Tour title, faces one of this tournament's biggest surprises in Hideko Tanihara of Japan.
"He looks unbeatable," Tanihara said. "I hope he doesn't feel good tomorrow, so maybe I have a chance."
Tanihara began the week by beating Jordan Spieth. On Saturday, he took down Paul Casey with two late birdies in the morning fourth round, and then he beat Ross Fisher, 4 and 2, to reach the semifinals.
None of Johnson's five matches had gone beyond the 16th hole. In the fourth round, he beat Zach Johnson, 5 and 4.
Haas is still amazed to even be playing. On Friday, he was on the verge of being eliminated when he hit into a hazard in a sudden-death playoff against K.T. Kim to decide their group. Haas took a penalty drop, chipped in from 120 feet for par to halve the hole and won on the sixth extra hole. Then he had to go 18 holes to beat Kevin Na in the fourth round before taking on Mickelson.
Haas made seven birdies in his match. He figured he will need something close to that number for his semifinal match against Rahm.
Fisher left with a consolation prize. By beating Bubba Watson in the fourth round, Fisher will move into the top 50 in the world and qualify for the Masters. Tanihara also was assured of being in the top 50 to get into Augusta National for the first time in 10 years.
Mirim Lee tops Kia Classic leaderboard
Mirim Lee shot a five-under 67 during the third round of the Kia Classic in Carlsbad, Calif., to go to 13-under and take a one shot lead over Mi Jung Hur, who made a 67-foot putt on No. 18 to card a 66.
Another South Korean, In Gee Chun, was tied at 10-under with Cristie Kerr, who was tied for the lead after the first round and was alone atop the leaderboard after 18 holes. Kerr, the 2015 Kia champion, had her most erratic round of the tournament, a one-under 71. Kerr, the 2015 Kia champion, had her most erratic round of the tournament, a one-under 71.
Brittany Lincicome made an early run with four birdies and an eagle in her first eight holes to get to 10-under before she had two bogeys on the back nine in a round of 67 that tied her with Austin Ernst and Karine Icher at nine under.
Stroud has one-shot lead in Puerto Rico
Chris Stroud birdied his final hole Saturday to cap off a five-under 67 and take a one-shot lead in the Puerto Rico Open as he goes for his first PGA Tour victory.
One shot behind was a pair of past PGA Tour winners, Bill Lunde and D.A. Points, who each shot 69.
The Puerto Rico Open is the 277th start of Stroud's career. The closest he came to winning was a playoff loss in the 2013 Travelers Championship. He lost full status on the PGA Tour last year for the first time since 2008.
Stroud was at 15-under 201 and has more than just Lunde and Points to worry about. Ten players were within three shots of the lead. Andrew "Beef" Johnston was among those two shots behind.
5:25 p.m.: This article has been updated with the quarterfinal round of play.