Defending French Open champion Garbine Muguruza believes there are 10 to 15 players who can challenge for the women's singles title this year.

Muguruza claimed her maiden grand slam crown at Roland Garros 12 months ago, stunning Serena Williams in the final.

And, with Williams pregnant with her first child and absent from the WTA Tour as a result, Muguruza does not feel there is a clear favourite to emerge victorious.

Asked about Williams not being at the tournament, Muguruza told a media conference: "I think it makes a difference, because if you look at the paper, Serena is always in the final.

"So for sure it makes a difference to not have her for a good reason.

"And I feel like there is 10, 15 girls that can win the trophy. So that's not normal. Before it is not like that. There was always like few favourites. It's kind of weird to have a lot more.

"But this year is very open. I feel like a lot of people can win."

Muguruza retired from a match with Elina Svitolina in Rome last week because of a neck injury.

Explaining her current physical condition, the world number five added: "I did a bad movement playing with somebody, and I still feel it. It takes a little bit actually to go away.

"With my team, with my physios, I feel for sure much better than Rome."