Golf: Dustin Johnson and Jon Rahm reach semifinals at Dell Match Play in Austin.

AUSTIN, Texas - Dustin Johnson answered a rare challenge and Jon Rahm delivered another early knockout Saturday to advance to the semifinals of the Dell Technologies Match Play, staying on track for a potential showdown between No. 1 in the world and golf’s brightest new star.

Johnson has looked so unbeatable this week that he led all 71 holes he had played until he lost a 3-up lead at the turn and was all square in his quarterfinal match when Alex Noren of Sweden holed a 40-foot birdie putt on No. 12.

Johnson answered with three birdies in four holes and won, 3 and 2.

Rahm was so dominant Saturday he played only 27 holes in two matches, and none of his last three matches have gone beyond the 14th hole. The 22-year-old rookie from Spain still hasn’t played the 18th hole since a practice round Tuesday.

After a 6-and-4 victory over Charles Howell III in the morning fourth round, he was even better in a 7-and-5 victory over Soren Kjeldsen.

Rahm said only his 65 in the final round to win at Torrey Pines was a better brand of golf.

“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 faces a semifinal match Sunday morning against Bill Haas, who ended Phil Mickelson’s hopes with a 2-and-1 victory in the quarterfinals. Mickelson had advanced to the quarters 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 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.

Tanihara began the week by beating Jordan Spieth. On Saturday, he took down Paul Casey with two late birdies in the morning, and then Ross Fisher, 4 and 2, to reach the semifinals.

PGA Tour

RIO GRANDE, Puerto Rico - Chris Stroud birdied his final hole to cap off a 5-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.

LPGA Tour

CARLSBAD, Calif. - Mirim Lee shot a 5-under 67 in the third round of the Kia Classic 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.