Simon Dyson's final-hole double bogey cost him a comfortable three-stroke lead and left him only one stroke in front heading into the final round of the 100th Spanish Open on Saturday.
Dyson flew the green with his approach shot but failed to get out of a bunker in regulation to finish with a 71 and his lead reduced to 5 under par.
Spain's Pablo Larrazabal (69) and Denmark's Soren Kjeldsen (71) shared second place.
Dyson was disappointed with his finish, describing his 6-iron from 180 yards out coming out like a bullet.
''I should be out of sight the way I am playing,'' he said. ''So it was a disappointing way to finish because for 17 3/4 holes I played really good.
''My shots all day, except for the last, were straight down the flags.''
Dyson is the highest ranked player in the field at No. 36 and is seeking a seventh European Tour victory.
If successful, it would be his ninth national open triumph in 10 pro victories to go with three Dutch Opens (2006, 2009, 2011), the Irish Open (2011), China Open (2000), Macau Open (2000) and Hong Kong Open (2000).
''I've still got a one-shot lead and while I should be out of sight in leading I will have to go out and enjoy the challenge again,'' Dyson said.
Larrazabal was in contention for a second straight year for his maiden win in his national open, and a week after winning a mini-tour event in his home city of Barcelona for his first success in Spain. Last year he led going into the final round but finished third.
''I played great today with three birdies in a row around the turn and just trying to stay patient, and even with a bogey at the last it is a great round,'' he said.
''This is a special tournament for me. Seve (Ballesteros) won it a lot of times, Sergio (Garcia) has won it and Alvaro Quiros won it here in Seville two years ago. So many of my heroes have won it.
''But tomorrow will be tomorrow and no matter what is my score tomorrow it will be fun.''
Despite criticism of the toughness of the Seville course set-up, Larrazabal was enjoying it.
''I like challenging golf courses and I don't like tournaments where the winning scores are 20 or 25-under par,'' he said.
''I like to fight for the scores and I like it when the conditions are tough like this and you have to manage yourself well to make pars.
''So I like the set-up of this week and I hope the wind keeps blowing again tomorrow.''
Kjeldsen, who turns 37 next month, fought back from a ninth-hole double bogey, to birdie three of his last six holes on the course where he captured his last victory, the 2009 Andalucian Open.
Spain's Jorge Campillo, also with a double bogey on his card, recorded a 73 to be lying fourth at 3 under.
Italy's Matteo Manassero carded a 76 to drop to a share of 12th place at 1 over but still only a stroke from the top seven. The 19-year old Manassero needs to be inside the top seven to be assured of contesting next month's US Open.
