The U.S. Open is the last big event of the year in international tennis. The late-summer championship in New York, the Australian Open, the French Open, and Wimbledon are known as the “Grand Slams.” Maria Sharapova, the Russian tennis star, has not played in a Grand Slam event since January 2016. After the Australian Open in 2016, she tested positive for a banned drug called meldonium. She was suspended from tennis for 15 months. Meldonium is thought to help the heart process energy more easily and allow athletes to play and practice harder without getting sore and tired. Sharapova returned to competitive tennis earlier this year after serving her punishment. On Monday night in New York, she defeated second-ranked Simona Halep of Romania in three sets.