Rory McIlroy made a strong start to the US Open to join a group of five players sitting just one shot behind leader Adam Hadwin.

Justin Rose and Matt Fitzpatrick are in contention on two under, while last year’s winner Jon Rahm shot a battling 69 at Brookline Country Club in Boston.

Benign morning conditions at Brookline saw 16 of the early wave finish under par, and that total increased to 25 with some fine performances from the afternoon starters in breezier conditions – including Hadwin’s round near the end of the day.

Just four strokes covers the top 41 players on a congested leaderboard, that includes Dustin Johnson lurking just behind the leaders on two under, but fellow LIV Golf competitor Phil Mickelson had a day to forget after shooting an eight-over 78.

Both players have been suspended by the PGA Tour for joining the new LIV Golf series, although the United States Golf Association, which runs the US Open, has allowed them to compete this week.

Six-time US Open runner-up Mickelson endured a miserable round on his 52nd birthday, as he had just one birdie against five bogeys and two double bogeys to leave him struggling to make the cut.

Hadwin’s 66 is his lowest score in a major in 63 rounds, and the first time the 34-year-old has led after any round of any of golf’s four biggest tournaments.

A flurry of five birdies in six holes on the front nine saw Hadwin hit the turn in 31, and he held on nicely down the tougher back nine with just one birdie and one bogey seeing him end the day at the top of the leaderboard.

“I was at ease, which is a nice feeling at the US Open as it doesn’t happen very often,” Hadwin told Sky Sports after his round.

“I had a good run there on the front nine but I knew there would be some tough holes coming home so it was just a case of hanging on.”

McIlroy sets the early pace as Fitzpatrick’s form continues

McIlroy arrived in Massachusetts full of confidence after winning a second successive Canadian Open on the PGA Tour on Sunday – and maintained his form with a solid round.

The Northern Irishman was leading on four under after 17 holes but missed the ninth green, his final hole of the day, and failed to get up-and-down from greenside rough to save his par.

It still represents a second consecutive strong start in a major for McIlroy, who shot 65 in the first round to lead the US PGA Championship last month before finishing eighth behind winner Justin Thomas.

“I’m feeling comfortable with my game,” the 33-year-old told Sky Sports. “Mentally I’m in a good place, which I think I showed out there with some of the par saves I made.”

Sheffield’s Fitzpatrick followed up his fine showing at the PGA Championship with a steady round of 68, but he walked off disappointed after also dropping a shot on his final hole.

Rose recreates Ryder Cup moment

Englishman Rose won the 2013 US Open on a similar type of course in Merrion Golf Club, and he is right in the mix again after his eventful round of 68.

Rose had just one par on his front nine, with three bogeys and five birdies – including one at 17 that was similar to Justin Leonard’s infamous putt in the 1999 Ryder Cup that was labelled ‘Battle of Brookline’.

Rose admitted when asked after his round that his celebration was: “100% Justin Leonard vibe.”

He added: “I was reading the putt, and I was, like, this is the putt Justin Leonard had. It went in with Justin Leonard’s speed. I don’t know if the camera stayed on me long enough, but I kind of had my hands in the air.

“I was going to run for a little longer like he did. It’s a little nod to Justin, but yeah, just trying to expel some European memories there.”

Darlington’s Tarren makes surprise start

One of the first players to finish was Tarren, who surprised everyone with a fine back nine propelling him to a 67.

Starting on the 10th hole, he played his first nine holes in one over par but birdied the first, fifth and seventh before an eagle on the eighth sent him out in front.

Tarren, who is 445th in world rankings, is playing his first season on the PGA Tour and appearing in just his second US Open after also playing at Pebble Beach in 2019.

The Darlington golfer qualified at Rattlesnake Point GC in Ontario, Canada, to take his place in the 156-strong field in Boston.

After also playing the Canadian Open, his clubs failed to make the same flight down to Massachusetts but finally arrived just before the event, which Tarren, 32, says he is fully enjoying.

“Every hole gets your attention. I’m loving being here this week,” he added.

“I’m excited with that start and let’s see what we can do with the rest of the week.”

Patience pays off for defending champion Rahm

Spain’s Rahm had to stay patient in an eventful first round that had a little bit of everything and almost got away from him after a fine start.

Rahm had three birdies in four holes on the front nine but struggled on the back nine and when one of several wayward iron shots cost him a bogey on 15, his frustration was evident.

However, the 27-year-old – who triumphed at Torrey Pines 12 months ago – kept his focus over the last two holes and dropped in a 21-foot birdie putt on the 18th to ensure he finished under par.

“That birdie on 18 was always going to change the energy of the round,” said Rahm. “I played really well the first seven holes, then when the wind picked up on the back nine, I struggled a bit.

“To make that birdie on 18 was pleasing because I hit a lot of bad iron shots the last 10 holes.”