|Tour Championship first-round leaderboard (US unless stated)|
|-13: D Johnson, J Rahm (Spa); -11: J Thomas; -9: R McIlroy (NI); -7: A Ancer (Mex)|
Rory McIlroy birdied his final three holes to stay in contention for a $15m (£11.3m) winner's prize at the PGA Tour's season-ending Tour Championship.
The 31-year-old shot a six-under-par round to reach nine under overall at East Lake Golf Club in Atlanta.
Players at the event are handicapped based on FedEx Cup points earned during the season, so McIlroy began seven shots behind top-ranked Dustin Johnson.
Johnson carded a round of three under and shares the lead with Jon Rahm.
Johnson and Rahm - world number one and two respectively - traded back and forth blows throughout to reach 13 under overall.
Rahm holed a huge putt on the 15th to move level with Johnson but the American drained a long putt of his own to regain the lead with his rival watching on.
Moments later on the 16th, Rahm moved to five under for his round with another birdie, which ultimately ensured they will start day two with a share of the lead.
McIlroy - who became a father for the first time earlier in the week - clawed back shots in the handicap system to win the Tour Championship in 2019.
This year he stuttered early on with three birdies and two dropped shots in his opening nine holes before finding five birdies on the back nine.
McIlroy also won the event in 2016 and a win this week would move him level with Tiger Woods' record of three victories at the Tour Championship.
How the Tour Championship works
Players amass FedEx Cup points during the season and the top 30 in the rankings contend the Tour Championship.
The top-ranked player begins the 72-hole tournament on 10 under par, while the second seed starts on eight under.
The third seed tees off at seven under and so on down to the fifth seed at five under. Seeds 6-10 begin at −4; seeds 11-15 will begin at −3; and so on, down to seeds 26-30 who will start at level par.