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

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

McIlroy was in one of the four winner-take-all matches between undefeated players. He and Kevin Na each missed birdie putts to win the match, and when they halved, they headed back to the first hole of a playoff. McIlroy won on the second extra hole with a 6-foot par after Na drove into a hazard.

McIlroy now has won 10 straight matches.