SOMETIMES all it takes is one match for all the anxiety and concerns to slip away. When Andy Murray arrived in Paris just under a fortnight ago after another early defeat in a disappointing clay-court season, there were many who expected his French Open campaign to be a short one.

Even the world No 1 himself had doubts but yesterday, Murray reminded everyone of the kind of form that took him to the top, with a 7-6, 7-5, 6-0 victory over Juan Martin del Potro to move into the fourth round.

Wins over Andrey Kuznetsov and Martin Klizan had been improvements on previous weeks but against Del Potro, whose forehand is one of the biggest weapons in tennis, he moved up a few levels.

“It was obviously an important win for me and a big match, because, Juan, when he’s playing well, is one of the best players in the world,” said Murray, who was dialled in from the start, concentrating well and moving smoothly against a man who he knew would give him problems.

“I maybe didn’t start the best, but made some adjustments, made some changes in the match tactically…that’s very positive, because I wasn’t doing that for the last few tournaments. In the last couple of matches I have done it and totally turned the matches around.”

Del Potro had admitted before the match that he was worried about a niggling groin problem which had affected him in his previous round.

But the Argentinian, who was playing at the French Open for the first time in five years after three wrist surgeries, began brilliantly, blazing massive forehands, breaking early on his way to a 5-3 lead.

Murray was also playing well and as his backhand began to find its range, he ramped up the pressure on Del Potro, saving one set point at 3-5 and another at 4-5 as he broke back to level at 5-5.

The two men held serve and then the tie-break was a mini-classic of its own as the Scot missed two set points at 6-4, saved two more at 6-7 and 7-8 and then finally won it 10-8 when a Del Potro forehand slid agonizingly wide.

The Argentinian hung his head and stood bent double over the net for all of 45 seconds, unable to believe he had let the set get away from him.

“It was just too much frustration,” he said. “I couldn’t believe that I lost that set, because I had many opportunities to win. I had been playing great, great points during whole, the first set.

“I could feel I was hurting him mentally. But it still was extremely complicated, because he was starting to return the balls better. My service was not hurting him as much anymore later into the game. He was a real No 1.”

The second set was almost a mirror image, minus the tie-break, as Murray went up an early break, couldn’t serve out the set at 5-4 but broke in the next game to take a two-sets-to-love lead.

The crowd on Court Philippe Chatrier chanted “Delpo, Delpo” but the big man was done and Murray romped through the third set to set up a clash with John Isner or Karen Kachanov, the young Russian having taken the opening set 7-6 before the rain came.

With Rafa Nadal and Novak Djokovic in the other half, Murray may just begin to fancy his chances of going one better than last year, when he made the final, but with Stan Wawrinka, a 7-6, 6-0, 6-2 winner over Fabio Fognini, a potential semi-final opponent, he is taking nothing for granted.

“I believe in myself, so even when things aren’t going well, I believe I can turn it around,” he said. “It’s not easy but if you do the right things in practice and trust it’s going to come if you work hard and do all the right things, then it generally does.

“I didn’t come here with the mindset that I’m definitely going to go a long way here. I was going to try and just get through the first round and hopefully feel better each day. That’s been the case so far.

“There were things I did today, that if I can do them consistently well over the next week or so then I could do really well. But I also know where I have come from. Even just 10 days or so ago, I was not playing well. So I need to respect that and work hard in practice and concentrate and if I do that, hopefully I can keep going further.”

Kyle Edmund was left with only the positives to take hold of after a tough five-set loss to Kevin Anderson, the South African, who came from two sets to one down to beat him 6-7, 7-6, 5-7, 6-1, 6-4.

“I played a good match and I’m disappointed to lose,” he said. “But I just have to talk about it, learn from it and keep moving forward.”