Connolly won her first Wimbledon title in 1952, defeating Louise Brough in the final. She had arrived at the tournament with a shoulder injury but refused to withdraw when Tennant instructed her to do so. The ensuing argument resulted in the end of their partnership. Connolly was seeded first at the 1952 U.S. Championships and successfully defended her title with a victory in the final against Doris Hart. For the 1953 season, she hired a new coach, the Australian Davis Cup captain Harry Hopman, and entered all four Grand Slam tournaments for the first time. She defeated Julie Sampson Haywood in the Australian Championships final and Doris Hart in the finals of the French Championships, Wimbledon, and the U.S. Championships to become the first woman, and only the second tennis player after Don Budge, to win the world's four major titles in the same year, commonly known as a "Grand Slam." She lost only one set in those four tournaments.