PGA Tour leaderboard LIVE: Latest from the FedEx Cup at the Tour Championship
Stanley shot a six-under-par round of 64 to send out a statement to the rest of the field.
The winner's share of the $35million (£25million) prize pool is $10m (£7m) and Jordan Spieth, who started the week in the driving seat after three consecutive top-10 finishes, is in the hunt to win the mega cash prize on offer.
And although he could play tactical golf in order to manage his position in the standings, Spieth insists he will still be going out to win the Tour Championship itself.
Express Sport recaps the first day of the Tour Championship, which is being hosted at Atlanta's East Lake club.
Latest leaderboard from the Tour Championship
"I'm comfortable at East Lake, and I'm in a great position.
"In 2014 and 2016 I remember being completely worn out by the time I got to the Tour Championship.
"There's a lot on the line. It's essentially a major after coming off a pretty hectic schedule in the last six or seven weeks."