Federer Looks for a Way Past del Potro After losing to Juan Martín del Potro in a heartbreaking five-set match in the United States Open final in 2009, Roger Federer did a rigorous post-mortem of the match and came up with a reason why he had lost. He served for a two-sets-to-love lead against del Potro, and seemed to have the match in hand. But del Potro hit a fantastic forehand passing shot that clipped the line to break Federer's serve, then seemed to gather energy and momentum as the match went on, besting a stunned Federer. Federer went to work on the glaring weakness that del Potro exploited, the Federer backhand. At 6 feet 6 inches, del Potro appears to be hitting downhill, leaning into his shots with unrelenting aggression. In that United States Open final, del Potro pounded the ball to Federer's backhand, working to either force an error or to get a short ball. He also made a shrewd adjustment on his serve that blustery day, opting to spin in a high-percentage first serve to deprive Federer of an opportunity to attack the second serve. The move suggested a tactical intelligence that Federer had not counted on. Del Potro laced into Federer's return, driving the ball relentlessly to the Federer backhand. Once exposed, Federer lost hope, and in a rare instance of poor competitiveness, he appeared weak and vulnerable by the end of the match. Federer repaired to the practice court. He spent the fall and winter of "09 and "10 working on his backhand. Like Bill Tilden, who spent a cold winter on an indoor court on Long Island to master the topspin backhand, Federer went to work on his weaker side. In his late 20s, Federer set out to bolster his backhand. The challenge was different from mastering Rafael Nadal's high-bounding topspin forehand. With del Potro, Federer had to counter the breathtaking pace that the Argentinean could generate. He practiced long and hard on how to hold his ground and go after the hard, flat ball attacking his backhand. Look for Federer to go toe to toe with del Potro in crosscourt backhand exchanges. He will also step in and tag some backhands down the line to sting del Potro. Watch how he takes a long stride across his body with the right leg to rip a backhand with remarkably efficient footwork. Federer's footwork is as simple as possible, but never too simple. For del Potro, this match is a return to the world's stage. His level of play in Melbourne has been astonishing. He dismantled Phillip Kohlschreiber in straight sets in the last round, signaling his rising level of play. He has shown extraordinary resilience in his comeback from wrist surgery, and Tuesday's match is one that tennis fans have been waiting for.