''I'm going shot by shot, hole by hole and trying to make as many birdies as I can,'' Larrazabal said.
The Spaniard, who won the tournament in a play-off with compatriot Sergio Garcia in 2011, finished strongly and holds a three-shot lead at 17-under par, with eight players tied for second on 14-under.
Larrazabal is yet to drop a shot in the tournament, but was nevertheless unhappy with his performance and he acknowledged that the wet course had been a factor.
''My game wasn't good today. I didn't hit the driver well. I put myself in a little bit of trouble but I knew how to handle it and to keep it going and make some birdies coming in. I can play better golf but - playing like I played, I cannot score better,'' Larrazabal said.
Emiliano Grillo would be closer to the Spaniard but for a double bogey on the final hole. The Argentine is tied with former winners Thomas Bjorn (2000 and 2002), Henrik Stenson (2006) and Robert Karlsson (1997), as well as Francesco Molinari, Carlos Del Moral, Rafa Cabrera-Bello and Richard Green, who catapulted himself into contention with the round of the tournament. The Australian made eight birdies and an eagle for a 10-under 62.
Green also alluded to the weather's impact.
''The course was firm on Thursday afternoon, bouncy, and now all of a sudden it's target practice now. So you can pretty much fly it at any pin and stop it right there,'' Green said.
Former winner Danny Willett, who started in a four-way lead with Larrazabal, Grillo and playing partner Cabrera-Bello, struggled with a shoulder injury. The Englishman made two bogeys, but recovered with two of his three birdies at the final four holes for a 1-under 71 to finish in a group at 13 under.