Horsey, who led the opening two rounds, shot a 2-under-par 70 on Saturday to reach 13-under 203 and was joined by Whiteford who shot a 66 at a sunny but windy Tseleevo Golf and Polo Club in suburban Moscow.
Horsey is one of just three players in the event ranked inside the world's top-200 and is seeking his third European Tour win, three years after his previous title.
Horsey had five birdies but also dropped three shots, and holed out from a greenside bunker to salvage par at the last.
"Pete (Whiteford) started like a train and I was just trying to tell myself to concentrate on my own game," said Horsey. "I just kept reminding myself to stay patient and concentrate on my own game, not what Pete was doing.
"I didn't quite maintain it that well on the back nine, but I kept myself in there and hopefully it'll be a little better tomorrow."
Whiteford is aiming for his first victory in his 181st tour event, having twice been a runner-up.
"It hasn't been the best season this year. It's been pretty brutal really," Whiteford said.
"I'm not confident at all but that front nine today helps massively and 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."
Pavan's flawless round of 64 was laced with eight birdies, including four in succession from the 13th hole. It set a new course record; one shot fewer than Northern Ireland's Michael Hoey posted en route to victory a year ago