Kevin Na built on an impressive second round to take the lead at the Charles Schwab Challenge on Saturday.

The two-time winner on the PGA Tour carded a one-under 69 in the third round to hold a two-stroke lead over the rest of the field.

Na, who carded the best round (62) of the tournament on Friday, played steady golf at Colonial Country Club in Fort Worth, Texas.

Na finished the day with three birdies, including two to open the round on the first and second holes. His only mistake came on the par-five 11th, where he had his first double bogey of the week.

He is nine under for the tournament.

"Over the years I've had some good rounds [at Colonial] and it's a golf course you don't have to overpower. You have to keep it in play," Na said, via Golfweek.com.

"From fairway in I'm a pretty good player, so I think it plays right into my game."

Right behind him is a star-studded tie for second place at seven under, including Jordan Spieth, Tony Finau and Jim Furyk. C.T. Pan and Mackenzie Hughes join them.

Spieth's game, including his putting, has been superb this weekend as he is chasing his first win since the 2017 Open Championship.

It is a good sign for Spieth, who had failed to finish inside the top 20 this year until ending up tied for third at last week's US PGA Championship.

Spieth also opened his round with birdies after a 29-foot putt on the par-five first hole and another 20-foot putt on the par-four second.

Charley Hoffman and Austin Cook are locked in a tie for seventh place at six under while Ryan Palmer, Nick Watney and Jonas Blixt – who was leading the field after 36 holes – are tied for ninth at five under heading into Sunday's final round.

Defending champion Paul Casey moved into a share of the lead at the halfway mark of the Valspar Championship on Friday.

Casey jumped 28 spots to take the lead at six under, alongside American Austin Cook.

Englishman Casey used an eagle on the par-five fifth hole and four birdies to card a round of five-under 66. Cook powered his way to first place behind five birdies.

But it is a congested leaderboard, with world number one Dustin Johnson just two strokes off the pace.

Johnson finished the day with one of the more colourful scorecards. He opened his day with a double bogey and bogey on his front nine, but closed out his round with five birdies and a bogey on the back to finish with a two-under 69.

Johnson sits in a three-way tie for sixth at four under with Curtis Luck and round-one leader Joel Dahmen. Between this trio and first place sits Luke Donald, Im Sung-jae and Scott Stallings in a tie for third.

Donald has been battling injury and has only made three PGA Tour starts this season. He even took a share of the lead at one point with a long birdie putt.

There is a sizable tie for ninth place at three under that has Jon Rahm in contention.

Rahm made a birdie-bogey-birdie start before levelling out. He was mistake-free for most of the day with three more birdies until a bogey on the par-four 18th hole capped off his round.

A number of golfers were close to not making the cut. Sergio Garcia, Henrik Stenson and Zach Johnson are just some of the names to inch by in a tie for 49th place at one over.

Some notable names to not make the cut were Gary Woodland – who missed the weekend for the first time in his last 23 starts to snap a tour-best streak – Keegan Bradley, Charl Schwartzel and Jason Day.

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