U.S. Open Round 1 grades

— -- PINEHURST, N.C. -- Pinehurst No. 2 was hard for everybody on Thursday. At times, it was difficult to tell the seasoned major champions from the teenaged competitors. But for the most part, these top-15 players in the official world ranking played some very solid golf.

These grades reflect the difficulty of the course and the grit these players demonstrated throughout their rounds.

None of them produced A work, but neither did any of them earn an F. Pinehurst No. 2 was a tough test, and these players have plenty of work to do on Friday and the weekend to improve their grades.

With a packed leaderboard and the margin for error so slim, any of them could easily be A students by the end of the week and perhaps even the 2014 U.S. Open champion.

Adam Scott    World ranking: No. 1 | Score: 73

The 33-year-old Australian has never had a top 10 in a U.S. Open in 12 appearances. HIs best finish in the championship was a tie for 15th in 2012 at the Olympic Club. On Thursday, after a birdie at the par-5 fifth hole to get to 1-under, Scott had four bogeys to finish with a 3-over 73. Still, he's far from being out of the tournament.

Henrik Stenson    World ranking: No. 2 | Score: 69

With a 1-under 69 on Thursday, the 38-year-old Swede had the best U.S. Open first round of his career. His ballstriking was superb. He hit 78 percent of his greens (14 of 18) and missed only four fairways. Certainly he would like to make more putts over the next few days, but it's a strong start for a player trying to win his first major.

Bubba Watson    World ranking: No. 3 | Score: 76

Bubba's chances of completing the Grand Slam in one calendar year might have ended on Thursday with a 6-over-par 76. The two-time Masters champion had five bogeys, a double-bogey at the par-5 10th hole and one birdie. Pinehurst No. 2 is no Augusta National. Donald Ross' baby punishes mavericks like Bubba and rewards those who play in a more controlled, disciplined style. It's not over yet for Bubba this week. He could shoot a great round on Friday and get right back into the tournament, but he can't shoot another 76 if he wants to even make the cut.

Matt Kuchar    World ranking: No. 5 | Score: 69

Rory McIlroy    World ranking: No. 6 | Score: 71

Jason Day    World ranking: No. 7 | Score: 73

Sergio Garcia    World ranking: No. 8 | Score: 73

Justin Rose    World ranking: No. 9 | Score: 72

Jordan Spieth    World ranking: No. 10 | Score: 69

Phil Mickelson    World ranking: No. 11 | Score: 70

The five-time major champion struggled on the greens with 31 putts, but he drove the ball well, hitting nine of 14 fairways on his way to an even-par 70. By his own admission, he could have shot a much lower score if he had converted a few of the makeable putts he had on Thursday. Still, it was good first round on a very difficult golf course.

Dustin Johnson    World ranking: No. 15 | Score: 70

The long-hitting eight-time PGA Tour winner played very solid on Thursday with a 1-under-par 69. He hit only half of his fairways, but he never got into serious trouble. Not surprisingly, two of his four birdies came at the par-5s, which he should dominate this week.