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Jordan Spieth has been the best player through the first 36 holes at the British Open, but many of his top rivals are close enough to the first page of the leaderboard that moving day at Royal Birkdale in Southport England should be a compelling experience.

Spieth started his round at six under par, and that was good enough to give him a two-stroke lead when he woke up Saturday morning. After battling rain and heavy wind the first two days of the tournament, the weather conditions were bright, sunny and calm and it left the contenders with a different mind set.

The excellent conditions Saturday helped Branden Grace set a record by firing an eight-under 62 in the third round. The South African golfer set the record for the lowest single-round score in any major tournament and is four under par through 54 holes

Dustin Johnson was also climbing the leaderboard in the third round, while Jason Day fired a five-under 65. That allowed him to reach even par after barely making the cut with a five-over cumulative score of 145 through the first two rounds.

Matt Kuchar, who started the round at four-under and was paired with Spieth in the final grouping of the day, told Steve Sands of NBC that it was time to change the game plan.

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"The first two days were all about surviving," Kuchar said on the NBC broadcast. "Today is much different, and it's quite amazing. It's a day to go out there and make some birdies."

It may be difficult for any of the golfers to catch Spieth, who was striking the ball well and also was the beneficiary of some good luck during the first two rounds. Nowhere was that more the case than the 15th hole during the second round. As he lined up to take his second shot on the par-5 hole, he attempted to launch a three-wood towards the green.

Instead of making solid contact, he hit the ball with the heel of his club. The shot squirted up the fairway and was basically a bouncing grounder that somehow skirted its way up the fairway, past the treacherous bunkers and came to rest on the green.

The ball was 18 feet from the hole, and Spieth nailed the putt for an eagle.

"I mishit the shot, which is probably why it looked so gross," Spieth said, per Doug Ferguson of the Associated Press (h/t Boston Globe). "I hit it low off the heel, which is easy to do when you’re trying to carve a cut. And it just ... one hop, scooted around the group of bunkers there, and then it was obviously fortunate to get all the way to the green.’’

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Spieth shot a 65 in the opening round and 69 in Friday's challenging conditions (howling wind and rain), and that gave him a two-stroke lead over Kuchar, and a three-stroke advantage over U.S. Open champion Brooks Koepka and Ian Poulter.

Koepka has played nearly as well as Spieth to this point in the tournament from tee to green. He was tied with Spieth after the first round, but he was unable to come through with his putter Friday. He did not have a birdie in the second round.

Koepka got through the first round with 21 putts, but it took him 31 strokes with the short stick to complete his second round, per Justin Ray of ESPN.com.

Spieth has already won the Masters and the U.S. Open during his career, with both of those victories coming in 2015. He also led the 2016 Masters midway through the final round before losing his advantage down the stretch.

A victory in The Open Championship would allow him to claim three of the four major championships before the age of 24. The only other player to make that claim is Jack Nicklaus.

If Spieth can win the Claret Jug at Royal Birkdale, he will be in a position to complete the career Grand Slam later this summer at the PGA Championship.

Rory McIlroy is also in a position to make a run at the British Open, something that did not look like a possibility through the first six holes of the tournament. McIlroy was five-over at that point before he managed to shake out of the doldrums. He finished with a 71 in the opening round and kept the momentum going with a 68 in the second round and that gave him a score of one under par through 36 holes.

"To be in after two days and be under par for this championship after the way I started, I'm ecstatic with that," McIlroy said, per Ferguson.

The birdie fest Saturday allowed golfers to climb the standings in the early going, and it left the leaders ready to take the baton and attempt to match or exceed those performances.