|Tour Championship first-round leaderboard|
|-4 H Matsuyama (Jpn), K Chappell, D Johnson (both US); -3 K Kisner (US), S Kim (Kor), J Day (Aus); -2 J Thomas, J Spieth (both US), P Casey (Eng), R McIlroy (NI); -1 M Kuchar (US), A Scott (Aus)|
FedEx Cup leader Dustin Johnson shared the overnight lead at the Tour Championship in Atlanta, with Rory McIlroy two shots off the pace.
Johnson, Hideki Matsuyama and Kevin Chappell carded four-under-par opening rounds of 66 at East Lake, as McIlroy recovered from three-putting the first.
Johnson will secure the $10m (£7.7m) prize money on offer in the FedEx Cup if he wins in Atlanta, with a top-five finish likely to be enough.
McIlroy must win to have any chance.
Johnson, who won the US Open in June - birdied three of the first six holes and then the last, after a 359-yard drive, to move into a three-way tie for the lead.
"I know there's a lot on the line, but there's a lot on the line every week," said Johnson.
"I come out with the same mentality. I felt really relaxed out there all day."
McIlroy, who needs to win and hope Johnson finishes tied second or worse, bogeyed the first and hit sixes at both the seventh and eighth holes during a rollercoaster round.
But seven birdies in total, including four in a row from 12 to 15, put him back into contention.
"It would be OK for the Ryder Cup next week I think, playing like this," McIlroy said on Sky Sports.
"I said to JP [Fitzgerald, his caddie] out there, I am mixing a lot of bad with a lot of good so if I can eradicate the mistakes, seven birdies around this golf course is pretty good and as you can see, once I get a couple of birdies I get some confidence and momentum."
Jordan Spieth, who won the FedEx Cup last year, also hit 68 to sit level with McIlroy on two under par.
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