A round of 68 gave Peter Uihlein the halfway lead at the Spanish Open in Valencia today.
Chile's Felipe Aguilar had carded 17 pars and just one birdie to finish on five under par at El Saler and was briefly joined at the top of the leaderboard by France's Raphael Jacquelin and Swede Rikard Karlberg.
But American Uihlein ended the day out in front with a birdie on his final hole to finish the day six under par, moving the joint leaders down into a three-way share of second place.
Shane Lowry and David Higgins head the Irish challenge on level par, with the latter shooting a disappointing 75 after having made a bright start to the event.
Jacquelin began the day five shots off the lead shared by Aguilar, France's Gary Stal and Morten Madsen, but equalled the lowest round of the day with a 66 containing seven birdies and just one bogey on the 17th.
Karlberg looked like taking the lead into the weekend when he raced to the turn in 31 with an eagle and three birdies in his first four holes before picking up further shots on the 11th and 14th.
But the tough closing stretch claimed another victim when he bogeyed the 17th and 18th and had to settle for a 67.
"I played good," Aguilar, who has won more than 30 tournaments in his native Chile but just one, the 2008 Indonesia Open, on the European Tour, told European Tour Radio.
"I had a bogey-free round with only one birdie and you could think it was a boring round, but it was quite exciting. I had a couple of bad shots and had to chip out and get up and down.
"Patience was key. I knew it wasn't going to be easy but I am quite comfortable playing right now. It's a long way to go and the weekend usually gets tougher. The greens are getting very hard."
Spain's Gonzalo Fernandez-Castano, 20th in the Masters at Augusta on Sunday, is three off the lead after a 73, while world number 13 Sergio Garcia is only six off the pace on one over after matching his compatriot's score.
"It was windy from the beginning so it was tricky," said Fernandez-Castano, who carded a 69 on Thursday. "I didn't play as good as I did yesterday, I hit a couple of loose shots that cost me but overall I have a chance. I need a good weekend but I am still in the tournament.
"It's just what is happening to me the last few tournaments, a great start and then I seem to be falling apart throughout the week. Hopefully I can get my act together and play well on the weekend. I'm going to need to play my best to have a chance on Sunday."
Miguel Angel Jimenez, playing his 599th tour event on his return to action after breaking his leg skiing in December, could only add a 74 to his opening 76 to miss the cut, while defending champion Francesco Molinari - suffering from a back injury - also bowed out after finishing seven over.