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Rickie Fowler may be leading the U.S. Open after carding a seven-under 65 in the first round at Erin Hills, Wisconsin, but a massive group of golfers is chasing the 28-year-old.

A record 44 players finished under par in the first round on Thursday, which beats a 27-year-old tournament record, per Sean Martin of PGATour.com:

That group doesn't even include golfers such as Adam Scott, who registered an amazing finish to land at even par, and 2015 U.S. Open champion Jordan Spieth, who didn't play his best golf but still managed to float above water at one over.

This tournament is already off to an exciting start, and we should be in for a treat this weekend.

Here is a look at the leaderboard, some second-round viewing information and three contenders who could take over top spot from Fowler and win the U.S. Open.

Leaderboard

U.S. Open Second-Round Viewing Information

FS1 will televise live coverage of the U.S. Open from 11 a.m. to 6 p.m. ET before tossing it over to Fox from 6 p.m. to 9 p.m.

Fans can also live-stream the U.S. Open online by following this link. The official U.S. Open website will show four featured groups throughout the day, including Fowler and other big stars. Furthermore, the action on the 13th through 15th holes will be shown for all groups as well.

Three Contenders To Watch

Paul Casey

Paul Casey routinely hangs around the top of the major leaderboards. In fact, he's finished in the top 10 nine times, including the last three Masters tournaments.

U.S. Open success has always seemed to evade him, however, as he hasn't finished higher than 10th since 2007.

However, this year could be the ticket for the Englishman, as he shot a six-under 66 on Thursday to vault into a tie for second place.

Every part of Casey's game was on point in the first round, especially his approach shots, as the PGA Tour official Twitter account showed:

The 39-year-old, who finished his round with six birdies and an opening-round eagle on the first hole, was 13th on the PGA Tour in strokes gained: tee to green this season prior to the U.S. Open and finished no worse than 22nd in his last five events.

Given his good form and impressive major track record, expect to see Casey back near (or at) the top of the Sunday leaderboard.

Tommy Fleetwood

Tommy Fleetwood was tied for first place at five under before Fowler pulled away with two late birdies.

If not for Fowler's heroics, much more attention would be placed on the 26-year-old, who played a flawless round with five birdies and no bogeys.

The European Tour's official Twitter account noted just how well the Englishman played on Thursday:

He has posted a nice season so far, winning the Abu Dhabi HSBC Golf Championship and finishing second by one stroke to Dustin Johnson at the WGC-Mexico Championship.

Fleetwood is the leading European Tour player in greens in regulation at 84.44 percent, per CBS Sports. He is also 16th in driving accuracy.

Like Casey, Fleetwood looks like he will be in this tournament for the long haul.

Adam Scott

It may seem odd to call Scott a contender when he is seven strokes back of the leader. However, there are three days left in the tournament, and the momentum he picked up after his scorching finish on the final four holes may carry over into the rest of the weekend.

Scott was four over going into the 15th hole before he notched back-to-back birdies. After a par on the 17th, the Australian then drained a 45-foot putt to break even on the day:

Since the beginning of the 2011 season, Scott has finished in the top 10 an astonishing 12 times and the top five seven times. The 36-year-old has also made every cut but two, with his last miss coming at the 2015 PGA Championship.

We could see Scott make a big charge up the leaderboard in the next day or two.