A blistering front nine helped Erik van Rooyen shoot a six-under 66 on Saturday to take control of the Irish Open.
The South African had shared the overnight lead at Ballyliffin Golf Club, but a run of three birdies in his first four holes, and three in succession between seven and nine, saw him reach the turn in just 29.
No further birdies followed on the way in, but the 28-year-old also avoided any blemishes to sit at 14 under for the tournament, giving him a four-stroke lead in outright first ahead of Sunday's final round.
Van Rooyen has already qualified for the Open Championship, which starts on July 19.
However, the three leading players not otherwise exempt who finish in the top 10 and ties will earn a spot in the field for the third major of the year at Carnoustie.
Among the hopefuls are Sweden's Joakim Lagergren and Ryan Fox of New Zealand, who are tied for second at 10 under.
A third round of 70 saw Fox give up a share of the lead, while Lagergren's 69 kept him in contention.
Frenchman Matthieu Pavon, the other member of the three-way share for top spot after Friday's second round, struggled to a one-over 73 and is now tied for sixth, along with countryman Raphael Jacquelin and England's Lee Westwood.
Ahead of them, 2016 Masters champion Danny Willett and Scotland's Russell Knox, who, like Westwood, have already qualified for The Open, are outright fourth and fifth respectively.
Andy Sullivan's seven-under 65 was the low round of the day, and he was joined by Spaniard Jon Rahm in a share of ninth at six under.
Rory McIlroy again underwhelmed, the four-time major winner's 72 leaving him one under for the event.