AUSTIN, Texas — Rory McIlroy had to go 20 holes. Jason Day only played six. Both advanced Friday to the round of 16 in the Dell Match Play.

Day was all square in his match when Paul Casey withdrew because of a stomach illness that has been bothering him the last two days. Day was likely to advance, anyway, but the short day at Austin Country Club at least allowed him extra rest for his back and for the weekend ahead.

Day has played only 31 holes in three days.

“If I can make it all the way through Sunday, that means I’m playing 72 holes on the weekend, which is a lot of golf,” Day said.

Phil Mickelson also had a short day and was headed home. Patrick Reed holed out for an eagle on No. 10 to go 7 up, and Mickelson did well to get to the 14th hole before Reed closed him out, 5 and 4. Reed has never trailed in any match all week.

McIlroy, Chris Kirk and Byeong-Hun An all played plenty of golf.

McIlroy was in one of the four winner-take-all matches between undefeated players in their groups, and it was a struggle from the start against Kevin Na. McIlroy, the defending champion, didn’t take the lead until the 15th hole, then gave it right back, and both missed birdie putt on 18 to halve their match.

It ended on No. 2, the second extra hole, when Na hooked his tee shot into a hazard and McIlroy holed a 6-foot putt for the win. He now has won 10 straight matches dating to his victory last year at Harding Park in San Francisco.

“I was dying after 10 holes, but I knew I’d played the back nine well,” McIlroy said. “It is a sign of relief. It’s nice to get to the weekend.”

PGA: Rafael Compos held onto the lead in front of his home fans in the Puerto Rico Open, shooting a 1-under 71 in windy conditions Friday.

The 27-year-old Compos had a 9-under 135 total at Coco Beach in Rio Grande for a one-stroke lead. One of two players to play in all nine editions of the event, he opened with a 64 on Thursday.

George McNeill, the 2012 winner, was second after a 71.

LPGA: Jenny Shin took the lead in the Kia Classic at Carlsbad, California, a stroke ahead of top-ranked Lydia Ko and Brittany Lang.

Shin birdied five of her first eight holes and had a 7-under 65 to reach 10-under 134 at Aviara in the final event before the major ANA Inspiration next week. The 23-year-old South Korean player is winless on the LPGA Tour.