Paris - Defending champion Stan Wawrinka reached the French Open quarter-finals at Roland Garros on Sunday with a 7-6 (7/5), 6-7 (7/9), 6-3, 6-2 win over Serbia's Victor Troicki.
It was the 31-year-old Swiss player's 11th straight win in the year's second Grand Slam and it puts him into a last eight match against Spanish surprise Albert Ramos-Vinolas, who upset eighth seed Milos Raonic in straight sets.
"It was far from easy with tough conditions -- heavy and cold, but I am happy to have come through it," Wawrinka said.
"It was a big battle, but I was able to stay calm and win this match."
Troicki saved four first set points at 5-6 but he was powerless to prevent Wawrinka running away with the ensuing tie-breaker 7-5.
It was Troicki, however, who stayed the more focussed at the start of the second set, breaking Wawrinka's serve in the fourth game to take a 4-1 lead.
Wawrinka, who also won the 2014 Australian Open title, reacted immediately with a break of his own to level at 4-4.
With light rain starting to fall on a sombre Philippe Chatrier centre court, it needed another tie-break to separate the players, Troicki levelling on his fifth set point.
Wawrinka, who needed five sets to get past Lukas Rosol in the first round, shrugged off that setback to take a 4-1 lead in the second after which Troicki received courtside medical treatment for a right thigh injury.
The Lausanne-based title-holder wrapped up the set 6-3 and he opened the fourth with another break to condemn his visibly wilting opponent to a fifth straight defeat at his hands.