Hideki Matsuyama opens up healthy five-shot lead at St Jude Championship
Matsuyama, the 2021 Masters winner, is on 17-under for the tournament with 20-year-old American Nick Dunlap five shots back and Norway's Viktor Hovland on 11-under.
The event is the opening of the three FedEx Cup playoff tournaments and current Cup standings leader Scottie Scheffler, who shot 69, is tied for fourth with fellow American Sam Burns, both seven strokes behind Matsuyama.
Matsuyama's round got off to an eventful start with a birdie on the par-4 first and a bogey on the par-4 second before an eagle on the par-5 third set him on his way.
He was outstanding on the green as he made four more birdies to open up his lead.
Matsuyama said his decision to change putters had paid off for him.
"I did put a new putter in the bag, and it has been behaving very well. I've had the putter for a while, and I thought, well, it might be a good week to debut that putter. But I might change putters tonight even," he said.
The Japanese, looking for his 10th win on the PGA Tour and his second this season after winning at the Genesis Invitational in February, will be wary of the lurking Scheffler, however.
Reigning Masters champion Scheffler, fresh off his Olympic gold medal in Paris, believes he remains in contention.
"Going into tomorrow, I'll do what I can to put some pressure on Hideki, but if he goes out tomorrow and shoots another 5-, 6-under, he's going to be a pretty tough guy to catch. But I'm definitely not totally out of the tournament," he said.
Hovland, looking to defend his FedEx Cup title, is in a similar situation and was hugely impressed with the way Matsuyama performed on a course that is challenging.
"It's super impressive stuff. It was not easy out there today," he said.
"It was a decent amount of wind and it feels like fairways are firming up a little bit, harder to hit the fairways, and with some of those pin locations being tucked pretty close to the edges, it's hard to be pretty aggressive into some of those flags.
"He's obviously making it work and I kind of tried to play just reasonable and not safe but just good strategy the whole way. I didn't make that many putts. If I would have got my putter going like I did yesterday, probably would have been a very similar score."
McIlroy fires 74
It was another disappointing day for Rory McIlroy, who shot a four-over 74 after starting on the back nine and making double bogeys on the 12th and the 13th.
McIlroy is five-over for the tournament, although he can at least look down the leaderboard at another former major champion, Jordan Spieth, whose 74 left him in penultimate position on seven-over.
The 70-strong field in the playoffs will be cut to 50 for next week's BMW Championship at Castle Rock, Colorado and then slimmed down further to 30 for the final event, the Tour Championship in Atlanta starting on August 29th.