Serena Williams underlined her determination to return to the top of women's tennis with a crushing win over Anastasia Rodionova.
Williams, 29, marked her first match on US soil since 2009 by beating her Australian opponent 6-0 6-0 at the Bank of the West Classic in California.
The 13-time Grand Slam champion is coming back from a series of injuries and said she was now focused again.
"I've always said if I play my best no one can beat me," she said.
"Hopefully I can get back to that level."
Williams has only played a handful of matches since her comeback from foot surgery and life-threatening blood clots which she said left her on her 'death bed'., and was beaten in the fourth round at Wimbledon last month by France's Marion Bartoli.
The defeat saw her fall to 175th in the world rankings, her lowest position since 1997, although she has since moved back up six places.
"Personally I have never taken this much time off," added Williams, following her 'double bagel' success against world number 105 Rodionova.
"Maybe this whole thing is teaching me to be patient.
"And it'll come. No. 1 is great, but I really want to be able to do well in the Grand Slams."
Her opponent in the second round will be Russia's Maria Kirilenko, the world number 25, who won 6-2 6-3 against sixth-seeded Julia Goerges of Germany.