Ekaterina Makarova knocked fellow Russian Vera Zvonareva out of the WTA Pattaya Open in Thailand on Wednesday.
The duo are close friends but there was no sign of that as Makarova cruised to a 6-0 6-2 victory in the second round to seal her place in the quarter-final.
Fourth seed Makarova needed only 63 minutes to see off the former world number two, who on Tuesday won her first game since returning from a 17-month injury lay-off.
Zvonareva, winner of this tournament in 2009 and 2010, made the worst possible start as she was broken in the first game of the match, and never recovered.
The 29-year-old had no answer to world number 28 Makarova's ground strokes and won only three points on her own serve in the first set.
Zvonareva, now ranked 992 in the world following her long absence, failed to fair much better in the second set and was unable to take advantage of the solitary break opportunity that came her way as Makarova comfortably progressed.
Sabine Lisicki and Svetlana Kuznetsova, the top two seeds, pulled out of the tournament due to injury on Tuesday, so Makarova will fancy her chances of going all the way.
Third seed Sorana Cirstea remains in the hunt to win in Thailand after beating Alison Riske 6-3 6-4 in the second round.
Romanian Cirstea was broken in her fourth service game in the opening set, but immediately broke back and served out the set in the following game.
She then broke the American in the opening game of the second set and served out the match, needing just the one match point to go through.
Cirstea will face Karolina Pliskova after the Czech came from a set down to beat Alla Kudryavtseva 4-6 6-3 6-4.