Seamus Power leads the FedEx St. Jude Classic at 5 under after 18 holes of play in Memphis, but two golfers with intriguing U.S. Open storylines next week are just behind him. Phil Mickelson and Brooks Koepka both shot 4-under 66s on Thursday in Memphis and are among a group of nine golfers one back of Power.

They combined for just three bogeys on the day as Koepka tossed in six birdies while Mickelson contributed three more plus an eagle on the par-5 3rd hole.

"I really, really enjoy this golf course," Mickelson said earlier in the week. "I think it's the most underrated on Tour. It just plays well. It just rewards good shots, it doesn't beat you up with length, it's a precision golf course. You have to be very precise. Nobody really runs away with it because it's hard to make birdies. It's challenging, but fair. Everything about it, I really enjoy."

Mickelson has never won here, but he has finished runner up in two of the last five iterations of this tournament. He and Koepka actually tied for second in 2016 when Daniel Berger won.

He's not unfamiliar with that second-place slot, either. Mickelson, who will play in the U.S. Open at Shinnecock next week as he searches for the career grand slam, has finished second there a record six times, including the last time it was played at Shinnecock in 2004.

Koepka, on the other hand, will go to Shinnecock as the defending U.S. Open champion. After missing time with a wrist injury earlier in the year, the reigning U.S. Open champion has played some incredible golf in his last few events. He has three 63s in his last six rounds and finished in the top 11 at both The Players Championship and the Fort Worth Invitational.

On Thursday in Memphis, he made four straight birdies in the middle of his round but felt unimpressed with his game overall.

"The putter got hot," Koepka said. "I felt like we drove it pretty well, we putted it really well. Other than that it was kind of sloppy, kind of ho-hum. I just needed to get something to build some momentum for this week."

Get hot, yes, but maybe not too hot. Remember, no player has ever won the U.S. Open after winning the previous week. The good news for Mickelson -- looking to become the sixth man to ever complete the slam -- and Koepka -- looking to become the first back-to-back champ of the Open since Curtis Strange in 1989 -- is that both are playing terrific golf heading into one of the four most important tournaments of the season.

They'll have plenty of competition over the next 54 holes, but Round 1 was the perfect start to the week for two of the biggest names in the game and two players looking to dial their games in for next week's big boy event in Southampton.