Serena Williams' coach Patrick Mouratoglou has described the American's return from maternity leave as "the biggest challenge" of her tennis life, but predicted she will be back to her best by the French Open. 

Speaking to ahead of the BNP Paribas Open at Indian Wells, which will be Williams' first tournament since scoring a 23rd major at the 2017 Australian Open, Mouratoglou said the 36-year-old has ambitions of winning the three remaining Grand Slams this season: the French Open, Wimbledon and the US Open.

"Serena's target [for this year] will be to win Grand Slams," said Mouratoglou, who has worked with Williams since 2012, and is also the founder of the Mouratoglou Tennis Academy. "She knows that coming back might take some time, but her level of expectation is high as always. There are three Grand Slams left this season. They will be her three main goals for 2018." Is this comeback the greatest challenge of Serena's career? 

Patrick Mouratoglou: It probably is. She is known for her comebacks, the last of which took place in 2012. Recovering from a surgery, then from a blood clot, going two years without winning a Grand Slam, she finally comes back at 30 years old to win 10 more Grand Slams and to stay No.1 in the world for three-and-a-half years - her longest period of dominance.

Now she is 36, just had a child, a second blood clot, has gone more than a year without any competition. I think we can say without a doubt that this is her biggest challenge.

What should everyone expect from Serena in the first few tournaments of her comeback? And what does she expect from herself?

PM: With Serena, it is always difficult not to expect her to win the tournament. But clearly we are in a very special situation at the moment. She hasn't played a match for more than a year, she has had a baby with a lot of complications post-delivery. The plan is to get back to her best level. She has been practicing hard for that, and competition is part of the process. She needs more than anything to compete and that is why she will plan to play Indian Wells and Miami.

We do not know how much time she will need to get her best level back, and I think that we should give her the necessary time for that without having too much expectations at the start.

When do you think Serena will be back to her best? 

PM: I think she will be ready for Roland Garros. The competitions she will play until then will help her and every day she progresses on her fitness.

How has becoming a mother changed Serena as a tennis player? 

PM: I think it is too early to answer that question. I do feel she is the same person once she steps on a tennis court. I can see during practices the same determination, the same level of expectation. There are two Serenas: the mother at home and the competitor once on the court.

Now I need to see her competing to be able to fully answer that question.

Serena Williams in action against Jelena Ostapenko at the Mubadala World Tennis Championshp in Abu Dhabi in December (Getty)

Have Serena's tennis ambitions changed since becoming a mother or is she still as ambitious as ever? Is she still driven by wanting to set the all-time Grand Slam record by winning 25 majors? 

PM: Serena’s life has changed. She has a family, she is a mother, she has different priorities now. But Serena stays Serena. When she decides to do anything, she does it to be the best in it.

Having a champion's mindset is not anything situational, it is an attitude, it is a trait of character. This always remains. She prepares herself to perform at the highest level.

She took the decision to come back to tennis. She definitely did not have to. Now she wants to break records again, and especially one. That is her drive, to keep winning Grand Slams and hopefully establish her own Grand Slam record. But she knows she will have to go step by step, it is a long way.

What are Serena's targets for this year? 

PM: Serena’s target will be to win Grand Slams. She knows that coming back might take some time, but her level of expectation is high as always. There are three Grand Slams left this season. They will be her three main goals for 2018.

What can Serena learn from other mothers, such as Kim Clijsters, who have returned to competition after having a baby? 

PM: Kim is a fantastic champion and a very inspiring person. I am sure that Serena has the highest respect for her. Kim showed that a champion stays a champion and that when you are able, after being a mother, to come back as fit as you were before, you can perform at the same level.

Has your admiration for Serena increased over the last few months? 

PM: No. I don’t think that my admiration for her can be higher than what it is. I am quite difficult to impress and to surprise, and I have always said that she constantly surprises me by doing things that are theoretically impossible to achieve.

Believe it or not, but after five years working together, she still surprises and impresses me often.

Read more: Serena's best chance of a 2018 Slam is Wimbledon, say Evert