"I didn't even remember how to slide anymore," said the Swiss superstar, when asked about the prospect of playing on the slow, red dirt in Europe this spring for the first time in three years. With its high bounces and often long and grueling rallies, clay-court tennis can be an added grind on the body. It is also the surface that least helps Federer's particular brand of attacking, first-strike tennis, even if has won 11 titles on clay, including the French Open in 2009. Federer last played at Roland Garros in 2015, when he lost in the quarterfinals to fellow Swiss and eventual champion Stan Wawrinka. But on his clay-court comeback at the Madrid Open Tuesday, he impressed with a 6-2, 6-3 win against Frenchman Richard Gasquet.Visit CNN.com/Sport for more news, features and videos
Federer's clay-court retirement began after an early loss in Rome in May 2016, and he pulled out of the French Open a few weeks later, saying he was not 100 percent fit. He missed the second half of the season to recover from a knee injury, having already had arthroscopic left knee surgery earlier the same year for a torn meniscus. In the past two years, he has given the clay a miss to focus on Wimbledon.But the 20-time Grand Slam champion is still firing on all cylinders, and keen to have "no regrets," he opted to make a return to the clay. Boosted by his 100th Tour title in Dubai in February, a runner-up spot in Indian Wells and victory in Miami, he approached he clay-court swing in confident mood. READ: Wimbledon prize money boosted to $3.06M for winners
At 37, though, Federer's return to the surface he grew up on in Switzerland was still somewhat of a surprise.Pierre Paganini, Federer's long-time physical trainer, had been apprehensive about the former top-ranked Swiss going back on the clay, telling the New York Times in 2017: "The disadvantage with the slide on clay is that in the joints there is a lot of vibration. We don't see it from the outside, but to control this slide there is instability in the knee, the foot, the ankle. And that in some cases can be bad for the knee or joint in question."Playing on clay, particularly in damp conditions, "places more stress on the player's cardiovascular system and also muscular endurance," because the balls become heavier, and the rallies longer, Ian Prangley, physiotherapist and physical coach for British No. 1 Kyle Edmund, told CNN Sport. "If a player hasn't maintained their aerobic fitness and endurance capacity during the hard court season, then that transition to longer clay-court points can be a problem," added Prangley.READ: Roger Federer's tears for former coach
'Ready for long rallies'
Ahead of his opening match in Madrid, Federer said: "You have to put in the hours on clay again. "You have to get used to sliding. It's about the different pressures that clay puts on your thigh and calf muscles compared with grass, for example. When you're playing on grass it's more about explosivity. "Here, it's a bit more about endurance. You just have to work on that. The work is difficult and it's hard. You have to be ready for long rallies and long matches, so you have to work on different things for your endurance."Federer made the decision to return to clay last December, he said, but only started practising on the surface at home in Switzerland last month, training at altitude to get used to playing in Madrid, which has an elevation of 650 meters.The knee, he said, is no longer on his mind. "I feel very strong right now," he said in Madrid. "Obviously we worked on that in December already. So the knee has been long gone, to be honest. That was all done by mid-17, I'd say, after I won Wimbledon."Prangley said the five-week preparation to the clay-court season will have allowed Federer to get his body in shape for the particular rigors of the surface, adding that he would have been working on his aerobic and endurance base, and strength.READ: Nadal suffers shock defeat by Fognini in Monte Carlo
Throughout his long career, Federer has remained relatively injury free, especially compared to his rivals Nadal, top-ranked Novak Djokovic anRead More – Source