Day 1 rundown: Takeaways from Thursday's U.S. Open action

Balls are in the air at the season's third major, with Day 1 action underway at the 122nd U.S. Open.

Follow along as theScore provides takeaways from The Country Club, starting with the early wave of players.

Another hot major start for Rory

There's no bigger star in golf right now than Rory McIlroy, and the 33-year-old again backed up his strong pre-tournament words with a brilliant 3-under 67 on Thursday.

After picking off four majors early in his career, McIlroy hasn't claimed one of golf's biggest prizes since 2014. The main culprit for that drought has been his scoring in the opening rounds. Since the beginning of 2015, McIlroy is 30-over in his opening rounds at majors while sitting 65-under in the other rounds combined.

However, the tide appears to be turning for McIlroy, as he held the first-round lead at last month's PGA Championship and sits just one back after 18 holes Thursday.

One of the biggest reasons for McIlroy's solid play Thursday morning was a clutch putter on the treacherous greens. In his victory last week in Canada, McIlroy was seventh in the field in strokes gained: putting, and he carried that quality to Brookline. The TOUR's 31st-ranked putter on the season canned five putts over 12 feet on Thursday, including three for par to avoid costly bogeys.

Mickelson's nightmare showing

Phil Mickelson's Thursday performance showed why it was probably a wise business move to join a golf circuit with guaranteed money.

The six-time major winner, who was celebrating his 52nd birthday, had a nightmare showing at The Country Club with an opening-round 78. He's currently ahead of just seven players in the 156-man field.

His jump to the LIV Golf circuit, and the manner in which he did so, has put Mickelson under the brightest lights in golf. After a disastrous performance at the inaugural event on the rival tour last week, Mickelson presented a very somber figure in his Monday press conference at Brookline.

That carried over to the golf course; he shot five bogeys and had a four-putt that led to one of two double-bogeys on the day. With the 8-over total, Mickelson is now 32-over in his last eight rounds at major championships.

He appears set to miss the cut for the third straight year at the U.S. Open.

Unlikely names in contention

Shoutout to anybody who had Adam Hadwin, MJ Daffue, Callum Tarren, or David Lingmerth on your betting card.

While Hadwin is known to PGA TOUR fans, he has yet to post a top-20 finish in 20 career appearances at major championships. Despite playing in the tougher afternoon wave, the Canadian posted the round of the day to grab the solo lead at 4-under.

The remaining trio of the No. 296th, 445th, and 592nd-ranked golfers in the world are among the group just one shot back at 3-under.

How shocking is it to see their names in contention? Daffue has never finished in the top 10 of a PGA TOUR event, Tarren has just one top-three finish worldwide since 2018, while Lingmerth doesn't have a top-10 showing since 2017. Daffue and Tarren don't have a Wikipedia page; Lingmerth's last entry came in 2016.

Daffue had the most eventful round of the trio with six birdies against three bogeys while Tarren made three birdies and an eagle to offset two bogeys. Lingmerth played solid golf throughout, avoiding a bogey en route to his 67.

JT in great shape again

Once again Justin Thomas finds himself in a great spot at a major despite playing in the tougher conditions of the day.

Fresh off an incredible weekend show at the RBC Canadian Open, the PGA champion turned in another solid performance with a 1-under 69 to sit just three off the pace.

The World No. 5 uncharacteristically struggled with the driver, ranking 109th in strokes gained: off the tee, well back of his 20th-place standing for the season. Thomas used brilliant approach play to put himself in quality scoring opportunities and took advantage with three birdies against two bogeys.

Thomas, who came from eight shots back to win his second major in May, will be among the first groups off the tee on Friday, with calm conditions expected that should lead to solid scoring.

Justin Rose roller coaster

Justin Rose came inches away from golf history on Sunday in Canada. However, a bogey on the final hole saw him fall one shot shy of shooting 59. Rose made an outrageous three eagles in that round with only five pars on the card - and just one on his closing nine.

The Englishman brought that style south to The Country Club, with an absolutely incredible opening nine at the U.S. Open.

Rose began his day on the 10th hole and made five birdies, three bogeys, and just one par en route to a 2-under 33. Combining that nine with his final nine in Canada and the 41-year-old played 18 straight holes at 8-under with just two pars.

Rose found some consistency on his final nine on Thursday, parring seven holes to finish two off the pace at 2-under.

Spieth stays in range with flu game

After being forced to cut his Wednesday practice session short due to stomach illness, there was some question as to whether Jordan Spieth would be well enough to make his early Thursday tee time. The three-time major champion didn't just show up on time; he showed up wearing white pants - a very bold choice for someone battling stomach issues.

It looked like Spieth would be undone by the stomach issues early, as the Texan bogeyed four of his opening five holes at the challenging layout. However, Spieth once again showed he's arguably golf's best battler by steadying the ship and mixing in four birdies to finish at 2-over, five back of the lead.

With a late tee time on Friday, the 28-year-old can rest and hopefully rid himself of the stomach issues to make a run in Round 2.

Rahm shows great fight to begin title defense

There were a number of loose iron shots, some questionable putting, and an F-bomb or two, but Jon Rahm began his U.S. Open title defense with a 1-under round of 69.

The Spaniard looked strong early with three birdies on his opening eight holes but faded down the stretch, heading to the 18th hole three back of the lead. He was battling a right miss with his irons and a balky putter, but last year's champ struck a brilliant iron on the final hole to give himself a chance to get under par for the day and post 69.

Rahm walked onto that green ranked 57th out of the 78 players in the early wave in strokes gained: putting, but he poured in the 21-footer for his fourth birdie of the day.

It certainly wasn't his best day on the course, but Rahm's ability to battle without his top stuff reminded us why he was a deserving champion last year.