- Roger Federer and Rafael Nadal among stars to pay tribute to Brad Drewett
- ATP's former president passed away on Friday after battle with illness
- Federer will be defending his title at the Madrid Masters this week
- Serena Williams begins defense of her title in women's event with win on Sunday
The stars of tennis took time out from their French Open preparations Sunday to honor the man who helped them become some of the highest-paid athletes in the world.
Brad Drewett passed away Friday, aged 54, succumbing to the motor neurone disease that had forced him to step down as head of the men's ATP World Tour.
Novak Djokovic, Roger Federer, Rafael Nadal, Andy Murray and Serena Williams led a minute's silence ahead of the start of the Madrid Masters, while similar tributes were held at tournaments in Portugal and Germany.
"Brad wasn't just the president of the ATP but was a player himself, a board member," Federer said on the ATP website.
"He's given so much time and effort to the ATP, and I think this is really what we will try to honor in a small way today."
Drewett reached a career-high 34 in the world rankings, but his efforts in administration had far bigger impact on the game, from his time on the players' council to running the ATP's Middle East, Asia and Pacific operations before becoming president in early 2012.
The Australian took the end-of-season championship to China as part of tennis' global spread in the early 2000s, and then brought it to London where it has become a lucrative moneyspinner and showpiece for the ATP.
He has also been credited with getting the players a larger share of prize money from the four grand slam tournaments since he took over the top role a year and half ago.
"He was always very nice to work with. Very honest. Very nice. Gentle," said 17-time grand slam winner Federer.
"I've really enjoyed every step of the way working with him. For me, it was hard seeing him not be the same anymore towards the end physically. But we can only appreciate what he's done for us and what he did until the last moment he really possibly could.
"That will never go away. I'm sure that the ATP and the players will come up with something for the legacy of Brad Drewett. It's very important."
Nadal said Drewett was "a very loved person" on the circuit.
"The only thing we can do is say thank you for everything he has done for our sport, all the support, and all the good things he has done these years to help us and to help us to have a better sport. It's a sad moment for all of us."
World No. 2 Federer is returning to action this week to defend his Madrid title, having recovered from the back injury that hampered him at Indian Wells in March.
Like Nadal, he is happy that the Spanish event has reverted to traditional red clay after experimenting with a blue surface last year that was roundly condemned by many players and subsequently banned by the ATP.
"There was a lot of criticism about the color, about the quality of the court as well, being extremely slippery," he told reporters.
"I don't know if that was due to the color, but this tournament has in the past had issues with the quality of the court. I think through what happened last year with the controversy around the blue clay, it was a big eye opener to have a proper court here now.
"I think this year, from what I'm hearing from the players, it's a good quality court and the players are happy. In the process, hopefully we'll see better tennis this year."
Top-ranked Djokovic, who ended Nadal's eight-year reign in Monte Carlo last month, is also happier with the new surface.
"The court is great. The one where I practiced is great. I haven't practiced on the center court yet, but I'll try to do that tonight to get a little feel about it," the Serbian said.
Nadal bounced back from his Monte Carlo final defeat to win the Barcelona Open title for the eighth time in nine years.
"The courts were not at the level to play professionally last year," he told reporters.
"Fortunately this year they are very good. In Madrid, we have the problem of the dry climate, so it's very difficult to have the clay that settles down properly."
The women's tournament is also packed with top names, as defending champion Williams seeks to protect her No. 1 ranking from the challenge of in-form Maria Sharapova -- who will go top if she wins the title.
Williams made a slow start to her opening match against Kazakh qualifier Yulia Putintseva on Sunday before winning 7-6 (7-5) 6-1.
However, her older sister Venus was forced to withdraw ahead of her match against Spain's Anabel Medina Garrigues due to a back injury.
Chinese fifth seed Li Na crashed out, losing 6-3 6-2 to 18-year-old American Madison Keys.
Former world No. 1 Caroline Wozniacki continued her decline, as the Danish 10th seed lost 6-2 6-4 to another Kazakh player, Yaroslava Shvedova.
Czech eighth seed Petra Kvitova, the 2011 Madrid champion, went through to round two along with Poland's world No. 4 Agnieszka Radwanska.
Meanwhile, veteran Tommy Haas won the Munich Open on Sunday, beating fellow German Philipp Kohlschreiber 6-3 7-6 (7-3) 13 years after losing in his previous final appearance in the clay event.
The 35-year-old, a former world No. 2, will now climb to 13th in the rankings.
It was the first all-German final in Munich since 1965, and Kohlschreiber was unable to defend his title -- having also won it in 2007.
In Oeiras, Stanislas Wawrinka upset top seed and world No. 4 David Ferrer 6-1 6-4 to win the Portugal Open on Sunday.
It was the 28-year-old Swiss' fourth career title, and first since January 2011.