The 48-year-old Furyk defeated Day two-up but the Australian former World No.1 was noticeably troubled in the last few holes at Austin Country Club on Wednesday.

He received medical treatment on his back immediately after the match and is a concern, not only for the remainder of the match play event in Texas but also The Masters at Augusta National in two weeks.

The latest issue comes three weeks after Day withdrew mid-round from the Arnold Palmer Invitational due to pain related to an annular disc tear.

He walked off the course after just six holes at that event and received four cortisone injections around his spine later that night.

However he was able to contest the Players Championship the following week and tied for eighth there.

Day, the 2014 and 2016 WGC-Match Play winner, blew a sizeable lead over American veteran Furyk.

He built a three-up advantage only to lose the next three holes with Furyk rattling off a trio of birdies.

The pair tussled for the remainder of the back nine before Day three-putted the 17th hole.

Day then uncharacteristically flubbed a pitch shot into a greenside bunker to lose the 18th hole and the match to former US Open winner Furyk.

RIGHT: Marc Leishman won his opening match against Kiradech Aphibarnrat. PHOTO: Ezra Shaw/Getty Images.

Countryman Marc Leishman got off to a winning start with a two-up victory over Thailand's Kiradech Aphibarnrat.

Leishman was inspired by a damning statistic for first-round losers at the WGC-Match Play since it adopted a round-robin format from 2015.

"I read a thing yesterday that in history of this format, only eight guys lost the first match and got through the group stage," Leishman said.

Fellow Australian Cameron Smith capitulated after building a two-up lead over Charles Howell through 12 holes, hitting his tee shot into the water hazard at the driveable par-4 13th.

He lost that hole and the next three to hand American Howell a 2-and-1 victory.

Meanwhile, Tiger Woods made a successful if unspectacular return to the event with a 3-and-1 victory over Aaron Wise.

The WGC-Match Play sees the top 64 available players on the world rankings seeded and divided into 16 groups of four players.

Each competitor plays three group matches with the winner of each section advancing to Saturday's Round of 16.

NOTABLE DAY ONE RESULTS AT WGC-MATCH PLAY

Dustin Johnson def Chez Reavie, 4 and 3

Justin Rose def Emiliano Grillo, 2 and 1

Lucas Bjerregaard def Justin Thomas, 3 and 2

Jon Rahm def Si Woo Kim, 7 and 5

Sergio Garcia def Shane Lowry, 4 and 2

Paul Casey def Abraham Ancer, 5 and 3

Francesco Molinari def Satoshi Kodaira, 5 and 4

Kevin Na def Bubba Watson, 1 up

- Evin Priest, Australian Associated Press