Birdie at 15 key for 'extremely pleased' Spieth

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Jordan Spieth highlighted a clutch birdie putt on 15 as crucial and said he "couldn't ask for much more" after opening up a three-shot lead over Matt Kuchar heading into the final round of The Open.

On a day that saw Branden Grace make history with the first round of 62 in a men's major championship, Spieth strengthened his own position by completing a faultless 65 at Royal Birkdale.

Having begun Saturday two clear of Kuchar at the top of the leaderboard, the 23-year-old Texan was able to add a stroke to his lead when he rolled in a lengthy birdie putt at the last and then saw his playing partner miss from much closer.

Yet it was an earlier putt that Spieth felt was particularly significant. After leaving an eagle attempt on 15 well left, the two-time major champion held his nerve to make birdie and ensure he remained one clear of Kuchar following the latter's four at the same hole.

"To knock that one in was the one that I thought was big to stay ahead," said Spieth, who is six clear of Brooks Koepka and Austin Connelly in third place.

"Because he [Kuchar] tied the lead there. I'd hit a good shot in and hit what I thought was a good putt and it ended up turning into not so good of a putt.

"And that putt [for birdie] was very difficult, because with any speed getting to the hole, the hole was on a crown, it was going to go three or four feet by, and then I've got a three- or four-footer for par for my putt. It was a scary one, probably the scariest of the day."

Softened greens and a lack of wind made for ideal conditions on Saturday, meaning Spieth knew he could not sit on his two-stroke overnight advantage.

"I thought being a very favourable day for scoring and recognising that ahead of time made it pretty tough mentally," he explained.

"I was in a position leading by two, where par being a good score, you'd think that would be just a little bit easier because you can play safer, which is how you want to play when you're leading. But it was a day where you had to be aggressive.

"It was a really solid round given the position we were in starting the day. I'm extremely pleased, couldn't ask for much more. Our goal was to shoot four [under] today."