Jordan Spieth, Rory McIlroy and Jason Day earn wins at the WGC

Rory McIlroy continued his unbeaten start to his WGC-Dell Match Play title defence, as Jordan Spieth and Jason Day also picked up their second win in as many days.

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Day two results from Austin

McIlroy twice came from behind to see of Smylie Kaufman 3&1 and stay joint-top of group 3, as world No 1 Spieth made a fast start on his way to a 5&4 victory over Ryder Cup star Victor Dubuisson.

Day completed the winning trio and erased concerns about his fitness in remarkable fashion, recovering from a back injury to eagle the par-four first and see off Thongchai Jaidee 5&3.

McIlroy, who left it late to defeat Thorbjorn Olesen in his opening group match, took the early lead when he holed a nine-footer at the second, only to hand Kaufman a slender lead after back-to-back blemishes over the next two holes.

Successive gains at the fifth and sixth helped McIlroy reach the turn one up, but he lost his cushion again with a par at the 10th and a wayward tee-shot in to the hazard at the 11th.

The tide turned in McIlroy's favour at the 13th as Kaufman found the water twice, with the world No 3 going back ahead with a two-putt par from 50 feet at the next.

A par on the 15th doubled McIlroy's advantage and, when Kaufman found more trouble on the 17th, he conceded the hole to give the Northern Irishman a 3&1 win to set up a group-three decider against Kevin Na on Friday.

In group one, Spieth's win sets up a winner-takes-all showdown with long-time friend Justin Thomas, while Day is guaranteed at least a play-off spot by sitting out on his own at the top of group two.

Day, who "tweaked" his back on the 15th during his victory over Grame McDowell on Wednesday and appeared to rub his back before hitting his opening tee shot, drove the 391-yard first green and holed a 12-foot eagle.

A conceded birdie at the next doubled Day's lead, before the Australian recovered from blemishes at the fifth and eighth to hole an eight-footer an reach the turn two ahead.

The world No 2 kicked off the back nine with successive gains to extend his advantage and sealed the win by rolling in from seven feet at the 15th.

Elsewhere, Bubba Watson picked up his first win of the week by beating Emiliano Grillo with a hole to spare and Dustin Johnson bounced back from an opening-day defeat to see off Kiradech Aphibarnrat 5&4.

Open champion Zach Johnson produced the biggest win of the day when he thrashed Martin Kaymer 8&6, while Matt Fitzpatrick's qualification hopes from group nine are over after a 4&3 loss to Patrick Reed.

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In the same group, Daniel Berger was forced to concede the final hole and the match against Phil Mickelson when he damaged his wrist as his club caught a rock.

The American had reached the 18th all square, only to pull his tee shot towards the rocks and fail to make contact with the ball during his downswing.

"I took a couple of practice swings and thought I had a clear swing," Berger told reporters. "It was kind of a shock. I have a good physio team so I will go to see them and hopefully I am good to go tomorrow."

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Andy Sullivan closed with back-to-back birdies to defeat Matt Jones 3&1, as Adam Scott registered a long-awaited win in the event by triumphing 3&2 over Chris Wood.

"It was a good match where we both played very solidly," Scott told Sky Sports. "We were back and forth for a bit but I just got the better of him at the end."

Watch the WGC-Dell Match Play throughout the week live on Sky Sports 4 - your home of golf. Live coverage gets underway on Friday from 6pm.