IF THERE is one thing Andy Murray will never be accused of, it is being a shrinking violet on the tennis court.

But though yesterday his rantings and mutterings were as frequent as they have ever been, his battling skills were never in question as he booked a place in the third round of the French Open.

The Scot’s 6-7 6-2 6-2 7-6 victory over Slovakia’s Martin Klizan, ranked No.50, was as hard-earned as the score suggests and featured numerous occasionally expletive-laden moments as Murray struggled against an inspired opponent who hits with enormous power.

But in what was a marked improvement from his efforts on clay this year, especially in Monte Carlo, Madrid and Rome, his heart and ability to find a way out of a difficult situation was clear for all to see.

Klizan, a left-hander who mixed massive forehands with deft drop shots, served for the fourth set at 5-4 but Murray stayed solid, breaking back and then clinching the tie-break 7-3 to set up a clash with Juan Martin Del Potro.

Having battled injury and more recently illness in the run-up to Paris, Murray was pleased with how he felt physically but also delighted with the way he changed his return position after the first set.

“I stepped way back on the second-serve return and was getting good height and depth on that shot and he was unable to dictate more of the points there,” said Murray, who said he felt he played a solid match.

“In the first set I wasn't doing that. I was stepping in and not getting a good hit on the returns. So that was another positive thing for me today, which I maybe hadn't been doing in Rome and Madrid, was when I was in a tough situation I found the solution, made some changes, and it worked out.”

In the first set, especially, when he looked a little heavy-legged, Murray spent as much time mouthing occasionally expletive-laden comments, sometimes to himself but more often in the direction of his support box, as he did into trying to combat the Klizan game.

Ivan Lendl and Jamie Delgado, his coaches, might have been better served wearing earplugs, the diatribe that came their way, and Murray admitted afterwards that it was a constant battle to improve the way he carries himself on court.

“Getting frustrated on the court is something that I have always battled with and always fought ever since probably since I was 20, 21 years old, and it's more venting,” he said. “Sometimes when I don't say anything, I come in and I get asked: ‘oh, you seemed very flat on the court’.

“That's just how I am. I feel like I have improved it from where I was in the middle of my career. It's something that I constantly try to get better.”

Despite that, there was some outstanding ball-striking, good movement, and good heart for the battle that Murray was delighted with as he prepares to face Del Potro.

“I definitely feel like I'm capable of winning that match,” he said. “I’m playing way better than I was two weeks ago, and today's match will have done me a lot of good, because physically I pulled up well and felt good, so I will gain a lot of confidence from that.”

Kyle Edmund made it two British men into the third round with a fine 7-5, 6-3, 6-1 win over Renzo Olivo, the man who beat Jo-Wilfried Tsonga in round one.

Edmund will now play South African Kevin Anderson, who upset Australia’s Nick Kyrgios in four sets.