He must beat Sahith Theegala on Friday and hope the unbeaten Spaun loses to Lee to set up a three-way play-off.

World number two Jon Rahm also remains in contention to progress.

The Spaniard, winner of three PGA Tour strokeplay events this season, beat Keith Mitchell 4&3 following his defeat by Rickie Fowler on Wednesday.

Rahm must defeat Billy Horschel in the final round of group matches to stand a chance of topping group two at Austin Country Club.

Former US Open champion Rahm ended American Mitchell's challenge with a fine run of three birdies and an eagle between the ninth and 13th holes.

On facing Horschel, who beat Fowler 3&2, Rahm told the Golf Channel: "Not many pairings are going to have more electricity on the course than me and Billy combined, so it should be a good one."

World number one Scottie Scheffler and Rory McIlroy, ranked third, are both in control of their respective groups after making it two wins from two on Thursday.

Scheffler won 5&4 against Alex Noren, while former champion McIlroy finished two up against Denny McCarthy.

McIlroy secured the win with a superb eagle on the 368-yard par-four 18th, driving his tee shot to four feet.

Elsewhere, England's Tommy Fleetwood suffered an early exit after tying his game with American Maverick McNealy. Fleetwood lost to JT Poston on Wednesday and the tied game against McNealy means he cannot qualify for the last 16.

Meanwhile, former Open champion Shane Lowry suffered an early exit as a 4&3 loss to Mackenzie Hughes ensured he cannot qualify as one of the 16 group winners.

Lowry could not recover as two bogeys in the first four holes contributed to him trailing Canadian Hughes by five after seven holes.

The Irishman will play Jordan Spieth on Friday, but it is Taylor Montgomery who is in control of group 12 after he beat fellow American Spieth 2&1 and now takes on Hughes in his final match.