Brooks Koepka will be chasing history at the PGA Championship on Thursday as the two-time defending champion attempts a rare major championship three-peat in San Francisco.

The 30-year-old American is seeking to join Walter Hagen as just the second player to win the major for a third consecutive year.

After winning the 2018 PGA Championship, Koepka successfully defended his title last year at Bethpage Black and is now aiming to become the first to win three straight since Hagen captured four in a row, beginning in 1924.

"My game feels like it's in really, really good shape right now," said Koepka. "I like the way I'm hitting it, and it feels like I am putting it really well.

"Every day is a lot more comfortable. I'm excited.

"This is a big-boy golf course. I think it kind of plays into my hands."

Golf's first major championship of 2020 will be contested without spectators after the season was placed on hold due to the COVID-19 pandemic.

Prior to its postponement on March 17, the PGA Championship was originally scheduled for play May 14-17.

This week was also the time set aside for the men's Summer Olympic golf tournament in Japan.

The US PGA Tour has been back, minus spectators, since early June but will really kick into high gear over the next couple of weeks.

More than a half dozen players and several caddies have tested positive in the eight weeks since the PGA Tour resumed.

Players, caddies and officials are tested for the coronavirus before entering the grounds. Players also undergo daily temperature screenings and their clubhouse has been redesigned to allow for three metres (10 feet) of space between lockers.

"Some sports are struggling to get their seasons going and things going and figure it out. Luckily the PGA Tour and the entities have been able to provide a safe environment with testing," said Spanish golfer Jon Rahm.

The PGA Championship launches the busiest phase of the disrupted season.

Following the PGA Championship are three weeks of FedEx Cup playoff events with the US Open on September 17-20 at Winged Foot near New York.

Lately when it comes to majors, the smart money has been on Koepka. But there is plenty of star power in San Francisco this week, including last week's Memphis tournament winner and new world number one Justin Thomas.

Two-time defending champ Brooks Koepka, of the US, looks on from the putting green during a practice round prior to the 2020 PGA Championship at TPC Harding Park
Two-time defending champ Brooks Koepka, of the US, looks on from the putting green during a practice round prior to the 2020 PGA Championship at TPC Harding Park GETTY IMAGES NORTH AMERICA / Harry How

"Last week is over with. This is a new week," Thomas said. "We have a new field, new guys that are out here, all trying to win a major.

"I'm trying to get rested more than anything. Get my energy back so we're ready to go come Thursday."

Thomas will tee off in a group with Tiger Woods and Rory McIlroy. Woods and McIlroy have already hoisted trophies at Harding Park.

Woods won the 2005 WGC-American Express Championship here, while McIlroy claimed the 2015 WGC-Dell Technologies Match Play. Thomas is playing here for the first time.

Four-time PGA Tour winner Woods is shooting for a record-setting 83rd PGA Tour victory. He can also become the first player in history to win majors in four different decades.

If Woods wants to capture his fifth career PGA Championship title and 16th major overall, he'll need his best game to show up, and for his aching back to hold up under the pressure.

"This is a big run for us coming up here. I've been gearing up for this, and looking forward to the challenges of not only this week, but obviously the playoffs and a US Open and then the Masters," Woods said on Tuesday.

Northern Ireland's McIlroy is one of several players who have held the world number one ranking at some point this season.

He has already won two PGA Championships, but his last one in 2014 also accounts for his last major title.

Rahm, Phil Mickelson and Sergio Garcia make up another marquee opening round grouping.

Rahm is coming off a recent victory at the Memorial Tournament and is trying to deliver on the big stage by claiming his first major championship.

"Hopefully I have it in me," Rahm said Tuesday. "Hopefully I've done the right things. Physically I feel great and mentally I feel like I'm great. I'm ready."

Three-time major champion Jordan Spieth needs to win the PGA to complete a career Grand Slam. With that he would join Gene Sarazen, Ben Hogan, Jack Nicklaus, Gary Player and Woods as the only players who have won each of the four majors.

"It's something that I really want," said Spieth, 27. "It's probably the No. 1 goal in the game of golf for me right now. I'd love to be able to hold all four trophies."

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