Dustin Johnson hits his second shot on the fourteenth hole at TPC Sawgrass in Ponte Vedra on Thursday. Photo: Tannen Maury/EPA

PONTE VEDRA BEACH – Dustin Johnson signalled he is not going to give up his world number one ranking without a fight after firing an opening round 66 to grab a share of the early lead at the Players Championship on Thursday.

Johnson's six-under-par effort was his lowest opening round PGA score in 13 months that saw him join fellow US Open champion and compatriot, Webb Simpson, along with Sweden's Alex Noren at the top of the leaderboard at Ponte Vedre in Florida.

Four players, including defending champion Kim Si-woo of South Korea, shared fourth place with five-under-par 67s.

Also at five-under was 26-year-old American Keith Mitchell who is taking the place of the injured Paul Casey, with the Tennessee-born Mitchell igniting his round with four opening birdies.

The 33-year old Johnson commenced his round from the 10th hole and raced to be six-under through 11 holes but then stalled to par his closing seven holes.

“I felt like it was a really solid day, I drove it really well, hit a lot of greens,” said Johnson. “I wasn't too sharp with the irons, but I still was on the green and rolled the putter very well.”

Dustin Johnson reacts as he putts on the fourteenth green in the first round of The Players Championship at TPC Sawgrass. Photo: Tannen Maury/EPA
Dustin Johnson reacts as he putts on the fourteenth green in the first round of The Players Championship at TPC Sawgrass. Photo: Tannen Maury/EPA

Johnson teed-up in the $11 million (9.2 milion euros) event with four players capable of supplanting him at the top of the world rankings.

“Every week Justin's (Thomas) pretty close, he's been pretty close to me for a while, so I mean every week I know there's a chance that someone can pass me,” added Johnson. “I definitely want to stay there, but if someone passes me it's not going to change anything, I'm going to still go back to next week and try to get it back.

“So, this week if I play really well I'll still be number one. If I don't, someone's going to pass me, which is okay.”

However, world number two Justin Thomas posted a one-over 73 while world number four Jordan Spieth struggled in signing for a three-over-par 75.

Included in Spieth's round was just two birdies but also four bogeys and a 13th hole double-bogey.

World number five Justin Rose, who needs to win at best to go past Johnson, signed for a four-under-par 68.

World number three Jon Rahm was out in the afternoon half of the draw.

Four-time Major winning Rory McIlroy again struggled with the putter in shooting a 71.