(CNN) -- Spain's Gonzalo Fernandez-Castano produced what he called the best round of his life to take the third-round lead in the Scottish Open at Loch Lomond on Saturday.
Spaniard Fernandez-Castano is bidding for his fifth European Tour victory in the Scottish Open.
Fernandez-Castano carded a seven-under-par round of 64 to lift him into a one-stroke advantage over German Martin Kaymer and South African Retief Goosen.
The British Masters champion, who is chasing his fifth European Tour success, told Press Association Sport: "That's the best I've ever struck the ball.
"Unfortunately my putting was not as good, but after a 64 I am not going to complain. It's funny. On the range I couldn't hit a shot. I hooked one five-iron 80 yards left of my target."
On the course, though, he started with three birdies, converted another chance on the ninth and posted three more birdies coming home.
Kaymer is looking for back-to-back wins following his French Open play-off success over Lee Westwood last Sunday -- and he did not drop a stroke either in a 66.
Goosen had been two in front of Adam Scott overnight, but after a smooth start bogeyed the 10th and 13th. However, a 69 was still far better than the Australian managed.
Scott, watched again by girlfriend Ana Ivanovic, mixed five birdies with five bogeys and a double bogey at the 415-yard 12th.
Welshman Jamie Donaldson moved up to joint fourth with Dane Soren Kjeldsen on 11-under, three strokes behind, after a 65 -- and is in position to claim the one British Open spot on offer from the tournament.
Fernandez-Castano did not have the only 64 of the day. Westwood produced the other to continue his brilliant recovery from a chest infection, which almost forced him out on Thursday morning.