The Briton faces Chela for place in semis, while Federer sets up showdown with Djokovic after overcoming Monfils in straight sets.
Andy Murray likes his chances against Juan Ignacio Chela
Andy Murray has admitted that his troublesome right ankle will be a source of concern when he meets the unseeded Argentine Juan Ignacio Chela today for a place in the French Open semi-finals.
Roger Federer moved on with a 6-4, 6-3, 7-6 (3) win over Gael Monfils to set up a showdown with No 2 seed Novak Djokovic.
"He [Monfils] is a superb player, so I knew the danger," said Federer after his sixth career victory over Monfils. "I'm very happy to be in the semi-finals."
The British fourth seed prevailed in five sets against Serbian 15th seed Victor Troicki in the fourth round, after an ankle injury sustained in his third-round win over Michael Berrer almost ended his tournament.
Murray fell two sets down against Troicki before fighting back to level the match Monday, and then had to battle from 5-2 behind to secure the final set when play resumed yesterday.
Troicki admitted he was a bit frustrated when, leading 3-2 in the fifth set, he was denied a 0-15 lead on Murray's serve when a ball boy mistakenly ran onto the court next to the net as the Serbian smashed an overhead past his opponent. The youngster then retreated in bashful fashion, while Troicki was left agog as the umpire ordered the point to be replayed.
It appeared to be Murray's day, especially when he realised as the match went on he could put more pressure on his ankle.
"The problem is if you go over on the ankle again," said Murray, who sprained his right ankle and sustained a partial tendon tear.
"That's the danger, because obviously it's weak just now … It's one thing I have to be careful with. Going over on it again would be an issue."
Murray has a 6-1 record against Chela, having beaten him at Roland Garros in both 2009 and 2010, and said the knowledge the Argentine was awaiting him in the last eight motivated his comeback against Troicki.
"No disrespect to any of the boys I've played with, but I thought it was a good chance for me to do well," said the three-time grand slam runner-up. "I've played Chela a few times here."
Murray beat Chela in straight sets at Roland Garros in 2009 before prevailing 6-2, 6-7, 6-3, 6-2 when they resumed hostilities in a rain-affected second-round match last year.
"When we played last year it was a tough match, with lots of long games. There was a rain delay, and we had to come back the next day," Murray said. "He's a tough player, one I've played well against in the past, and I'll have to do well against him again tomorrow."
The winner of the match will face either top seed and defending champion Rafael Nadal or fifth-seeded two-time runner-up Robin Soderling, who meet in today's other quarter-final match.