Britain's Andy Murray beat Viktor Troicki 6-3 6-2 to progress to the second round at the Rio Olympics.
After losing his serve in the first game, the defending champion went on to control the tempo of the match.
The 29-year-old Scot will return to begin his doubles campaign alongside brother Jamie later on Sunday.
Defending women's champion Serena Williams started her title defence with a 6-4 6-2 victory over Australia's Daria Gavrilova.
More to follow.