During the summer, he experimented with various different racquets and played the German Open with a blacked-out 98-inch Wilson racquet, instead of his regular Pro Staff 6.1 90 BLX racquet with the smaller 90-inch hitting area. He returned to his regular racquet for the second half of the season.[102][103] After Wimbledon, Federer continued to be upset early in tournaments in Hamburg and Gstaad because of a serious back injury through October, when he announced that he was parting ways with Paul Annacone, his coach for the last three years.[104] Federer made the final in Basel, succumbing to Juan Martín del Potro in three sets, and indicated it was a mistake to have played certain tournaments while suffering from a back injury.[105]