GIRONA, May 17, 2014 (AFP) - Jimenez had carded six birdies in 13 holes but then bogeys at the 15th and 18th holes gave him a 69 for the day and five-under for the tournament with Pieters knocking in birdies at 15 and 16 for a round of 71 and seven under.
"I'm a little disappointed with that," said 50-year-old Jimenez who is the oldest winner in European Tour history, beating his own record by winning the Hong Kong Open at the age of 49 years and 337 days last December.
But he has yet to win the Spanish Open.
"It would be nice. I'd love to win the Spanish Open of course and we'll see what happens tomorrow."
Pieters, 22, only turned professional in June last year and secured his European Tour card via the Qualifying School in November.
"It was a solid day. I hit solid shots and really played to my strengths. I got two over par early just because my short game wasn't sharp enough but I took advantage of the par fives again today and the shots dropped in the end," said the Belgian.
"I stayed really patient, you need to be on this course and I'm getting better and better at it. You know that it's going to be a hard day and an even par is a good score."
Leading Spanish Open third round scores at the par-72 PGA Catalunya Resort course on Saturday (GBR/IRL unless stated):
209 - Thomas Pieters (BEL) 69 69 71
211 - Miguel Angel Jimenez (ESP) 69 73 69
212 - Richie Ramsay 69 72 71, Chris Wood 73 70 69, Richard Green (AUS) 74 69 69
213 - Richard Bland 73 68 72, Felipe Aguilar (CHI) 74 70 69 Maximilian Kieffer (GER) 75 69 69, Ross Fisher 70 76 67, Joost Luiten (NED) 70 69 74
214 - Magnus A Carlsson (SWE) 72 74 68
215 - Francesco Molinari (ITA) 73 67 75, Robert Jan Derksen (NED) 69 74 72, Emiliano Grillo (ARG) 74 72 69
216 - Mikael Lundberg (SWE) 72 74 70, Alvaro Velasco (ESP) 75 73 68 Gareth Maybin 73 70 73, Mikko Korhonen (FIN) 74 69 73, Tom Lewis 72 75 69, Darren Fichardt (RSA) 77 66 73, Raphael Jacquelin (FRA) 73 72 71 Alexander Noren (SWE) 71 72 73, Paul Lawrie 70 72 74, Sergio Garcia (ESP) 69 74 73, Paul McGinley 72 72 72
217 - Marc Warren 75 70 72, Andrea Pavan (ITA) 74 72 71, Jordi Garcia Pinto (ESP) 70 73 74, Alejandro Canizares (ESP) 72 76 69, Wade Ormsby (AUS) 72 74 71, Alvaro Quiros (ESP) 74 67 76, Gregory Havret (FRA) 71 75 71
Selected
219 - Jbe Kruger (RSA) 70 78 71
221 - Thomas Aiken (RSA) 74 73 74
223 - Hennie Otto (RSA) 71 76 76, Gaganjeet Bhullar (IND) 71 74 78