Spieth aces, Casey grabs share of Challenge lead

World number one Jordan Spieth aced the par-3 second hole while England's Paul Casey fired a six-under par 66 to share the lead after round one of the Hero World Challenge.

Casey's bogey-free round put him alongside Americans Jimmy Walker and Zach Johnson atop the leaderboard at the 18-man event hosted by Tiger Woods.

Defending champion Spieth's shot of the day left him one stroke back on 67 alongside compatriots Bubba Watson, Bill Haas and Brooks Koepka and Australian Adam Scott.

Spieth, the reigning US Open and Masters champion, used a 6-iron from 172 yards for his hole-in-one and followed with a bogey-free round that included birdies at the seventh and back-to-back at the 14th and par-5 15th.

Casey, who suffered two playoff losses on the US PGA Tour this season, enjoyed his tour of the Albany resort, making birdies at the par-5 third, sixth and 15th holes. He also opened and closed the back nine with birdies and added another at 13 to secure his playoff among the leaders.

It's the seventh appearance at the event for Casey, who shared third in 2010 and 2011, his most recent prior starts.

Walker closed the front nine with a bogey to stand at level par but made six birdies on a bogey-free back side to seize his share of the lead.

Johnson, the 2013 Challenge champion, birdied three of the four par-3s -- the fifth, eighth and 17th holes -- as well as the 10th, 11th, 15th and 16th.

Scott birdied the par-3 second and eagled the par-5 third then answered a bogey at the fourth with a birdie on the par-5 sixth. On the back nine, he took a bogey at 13 but responded with back-to-back birdies at 14 and 15th and closed with another birdie to stay on the leaders' heels.