Samantha Stosur looked like a defending champion, not the player who has struggled often this year, in her first match at the U.S. Open.

The seventh-seeded Australian needed just 51 minutes to beat Petra Martic of Croatia 6-1, 6-1 on Monday in the tournament's first match at Arthur Ashe Stadium.

Stosur stunned Serena Williams in last year's final at Flushing Meadows with a straight-set win for her first Grand Slam title.

But in 2012, she lost in the first round of the Australian Open and London Olympics and the second round at Wimbledon.

On Monday against the 64th-ranked Martic, who withdrew from the Olympics with a left foot injury, Stosur had 22 winners and 10 aces and didn't face any break points.