Rather interesting, when all 7 of Agassi's titles in 1995 were on hardcourts, while Muster had won a masters title on indoor carpet in 1995, including a win over Sampras in the semi finals. As Muster said "I didn't win my ranking points in a supermarket. What do they want me to do, write the computer a letter of apology?" I think it happened on a much smaller scale in 2011. Nadal's form in 2011 was much better in Indian Wells, Miami, Wimbledon and the US Open than it was in any clay-court tournament that year, apart from the last few matches of the French Open. In 2012, however, Nadal was back to dominating on clay, whereas Muster in 1998 only managed a slight improvement on clay, and still didn't win a tournament, which was obviously nowhere near his dominance of 1995 and 1996, years where Muster won a combined 18 titles on clay. The initial injury was on hardcourts, as I've mentioned. It was at the US Open in 2001. That came after a summer of success on hardcourts for Guga as well. His 2001 Cincinnati draw was brutal, beating Roddick, Haas, Ivanisevic, Kafelnikov, Henman and Rafter in consecutive matches. He then reached the final of Indianapolis, beating Henman and Ivanisevic again, but retired against Rafter in the final.