Serena Williams opens gold medal defense with straight-sets win

Serena Williams opened defense of her Olympic singles gold medal with a patchy-at-times 6-4, 6-2 victory over Australia's Daria Gavrilova.

Sunday's match at the Rio de Janeiro games was Williams' first since she won her Open-era record-tying 22nd Grand Slam title at Wimbledon last month.

The American, seeded No. 1, was hardly at her best in the 91-minute contest, compiling 37 unforced errors to 27 winners, and she got broken at love while serving for the first set at 5-3. But Williams broke right back in the next game.

Williams is scheduled to play doubles with her older sister Venus later Sunday.

The younger Williams owns four gold medals - in singles at London four years ago, and in doubles in 2000, 2008 and 2012.