Kamila Valieva, the young Russian figure skater at the center of a doping fight at the Beijing Games, left the ice in tears after nerves and a series of tumbles in Thursday’s free skate cost her an Olympic medal. But her coach, the super-tough Eteri Tutberidze, was having none of it, as shown by a rinkside videoclip posted on Twitter but later deleted for a purported copyright breach. “Why did you let it go like that? Why did you let it go?” she asked the 15-year-old. “Why did you stop fighting? Well, explain. You let it go after the axel.” Tutberidze has produced a string of world and Olympic champions over the past decade, young women who have become known as the “Quad Squad” for their ability to master the most technically demanding jumps. Tutberidze had been hoping for a clean sweep of medals, and almost got it. Russians Anna Shcherbakova, the 17-year-old, and Anna Trusova won gold and silver, but Valieva’s faltering performance saw her drop into fourth place behind Kaori Sakamoto of Japan.