British Open Tournament 2017: Real-Time Leaderboard Updates for Thursday Leaders

Jordan Spieth has served notice that he is ready to make a legitimate run at winning the Claret Jug.

Spieth has shown signs of returning to an elite level in recent weeks, as he picked up a victory in the Travelers Championship in late June.

The two-time major champion took that momentum with him when he crossed the Atlantic and arrived at Royal Birkdale in Southport, England, to begin play in the Open Championship. Spieth made a sharp birdie on the second hole, and that propelled him to a five under par 65 in the opening round of the third major championship of the year.

U.S. Open champion Brooks Koepka remains on top of his game even though he has not competed since winning the national championship in June. He also shot a 65 in the opening round.

Spieth hit just five of 14 greens in regulation, but he made up for that issue by honing in on the flagstick with his approach shots. He was nearly infallible in that area, and that allowed him to post an impressive score on the first day of competition.

He did not have a single bogey on his card, and he was able to finish his round with just 29 putts. He labeled his opening round as a "nine out of 10," during a post-match interview with Sky Sports. 

"I drove the ball well which is very important out here," Spieth said. "When I missed my drives I missed them in locations where I could still hit the greens. From the middle of the greens out here you can putt and have a pretty good look at just about any hole."

Koepka thought that the break from competition was needed more than a few practice rounds on the links-style course. His game plan proved to be correct, at least in the opening round.

One of the reasons that Koepka believed he didn't need to get accustomed to the British course is that he had played on the European Tour for two years.

Koepka does not profess the love of the game that many players talk about. He told Sky Sports that golf can be a bore at times. 

"It just takes a creative mind and sometimes golf can get a bit boring but I see so many shots out here where it's fun and keeps me interested and really gets me going," Koepka said.

Dave Thompson/Associated Press

Ian Poulter and Justin Thomas were among the golfers who finished their first round at three-under, just two strokes behind Spieth and Koepka. 

Thomas' round featured an eagle on the 567-yard, par-5 17th hole, and he appreciated the difference between the links-style course at Royal Birkdale and the courses in the United States.

"It's so rare in the States where you are not trying to hit a yardage," Thomas said. "You just have to feel it. I feel as if I enjoy that aspect of it and think this is a great links course like the rest of them that I have played."

Hideki Matsuyama of Japan and Sung Kang of South Korea are among the golfers who finished their first round at two under par.