MOSCOW, July 26, 2014 (AFP) - Whiteford, who is yet to taste glory on the European Tour after two second place finishes, closed the gap on two shot overnight leader Horsey as both men finished the day on 13 under par after 54 holes.
"I had an amazing start. I holed a bunker shot on the first and then chipped in on the third. Dave (Horsey) chipped in as well - he stole some of my glory there", said Whiteford.
"So I got off to a flyer and then the back nine I was just hanging on for dear life. The swing didn't feel great at all to be honest. I'm hoping I wake up tomorrow with a better swing. I had a lot of good luck today."
Whiteford's round also included an eagle when he holed out from the bunker at the par five eighth at the Tseleevo Golf and Polo Club outside Moscow.
Horsey began well with birdies at one and three before a bogey at the ninth, where he found the rough, cost him his place at the top of the leaderboard.
He finished the day with a two under par 70.
"Pete (Whiteford) started like a train and I was just trying to tell myself to concentrate on my own game," said Horsey.
"It wasn't that easy out there today and I certainly didn't see a five or six under through nine holes. I just kept reminding myself to stay patient and concentrate on my own game, not what Pete was doing.
"I'm glad Dave and I have put a bit of breathing space between us and the next guys. It might be a bit like match play on the front nine tomorrow." added Horsey.
Andrea Pavan of Italy had the tournament's best round so far with an eight under 64 as he shares third place with Scotland's Scott Jamieson and Thomas Pieters of Belgium, four shots off the lead.
Leading scores after the third round of the EPGA Russian Open on Saturday (par 72):
203 - Peter Whiteford (SCO) 66 71 66, David Horsey (ENG) 65 68 70
207 - Andrea Pavan (ITA) 73 70 64, Thomas Pieters (BEL) 67 68 72, Scott Jamieson (SCO) 66 72 69
209 - Sam Hutsby (ENG) 72 67 70, Gary Boyd (ENG) 69 68 72, Damien McGrane (IRL) 69 71 69
210 - Jamie McLeary (SCO) 68 72 70, Soren Hansen (DEN) 72 69 69
211 - Maximilian Kieffer (GER) 67 71 73, Javier Colomo (ESP) 72 68 71, Adrian Otaegui (ESP) 70 73 68, Krister Eriksson (SWE) 72 68 71
212 - Adrien Saddier (FRA) 69 73 70, Jorge Campillo (ESP) 68 76 68, Edouard Dubois (FRA) 72 68 72
213 - Joachim B Hansen (DEN) 69 73 71, Sam Walker ENG) 69 71 73, Seuk-hyun Baek (KOR) 74 70 69, Brinson Paolini (USA) 72 71 70, Kevin Phelan (USA) 69 70 74, Haydn Porteous (RSA) 72 71 70, Gaganjeet Bhullar (IND) 67 71 75, Mikko Korhonen (FIN) 74 71 68
214 - Carlos Del Moral (ESP) 70 71 73, Roope Kakko (FIN) 71 73 70, James Heath 71 72 71, Adam Gee (ENG) 70 75 69
215 - Merrick Bremner (RSA) 79 65 71, Daniel Im (USA) 73 72 70, Mathias Gronberg (SWE) 70 70 75, Stuart Manley (WAL) 71 73 71, Gunn Charoenkul (THA) 73 68 74, Daan Huizing (NED) 72 74 69, James Morrison (ENG) 71 73 71, Oliver Bekker (RSA) 67 76 72, Andreas Andersson (SWE) 70 73 72, Richard Finch (ENG) 71 73 71, Alastair Forsyth (SCO) 75 70 70, Nacho Elvira (ESP) 69 69 77