Wawrinka not worried by back problem

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Stan Wawrinka says he is not worried about his back problem despite having to undergo treatment during his French Open fourth-round win over Gael Monfils.

Wawrinka disappointed the home crowd at Roland Garros by ending Monfils' hopes with a 7-5 7-6 (9-7) 6-2 victory on Monday.

The Swiss, a winner of the clay-court grand slam in 2015, underwent treatment on his back midway through the second set.

But, after edging the second, Wawrinka eased through the third to set up a meeting with Marin Cilic, and does not believe his back will be an issue.

"I blocked my lower back at the beginning of the match after one game. So I just wanted to fix it, to make sure it cannot get worse. That's why I call [for the trainer] at that moment.

"I have experienced this before. I'm not seriously worried. It doesn't keep me from playing, and it doesn't keep me from playing well. Let's put it this way: It's under control. That's what I would say.

"My back has always been a bit sensitive. I know I have to be careful about it, but again, it doesn't prevent me from playing very well. So it's not really important."

Garbine Muguruza left her media conference in tears when asked about a partisan home crowd during the 2016 champion's defeat to Kristina Mladenovic.

Muguruza's coach had labelled the French fans "pathetic" for their treatment of the Spaniard, but Wawrinka felt they were fair towards him.

"Well, I was expecting for him to have a lot of support. They love Gael here. He's playing at home, so it's [the support for Monfils] normal," he added.

"I was also quite surprised, was really good crowd. I think they were really fair on the court. I think the atmosphere was great to play, so I'm happy with everything."