Former world number one Serena Williams recovered from a set and three break points down to beat compatriot Bernarda Pera in her first match in six months.
The American, who has 23 Grand Slam singles titles, was in deep trouble when 4-6 and 0-40 down at 4-4 in the second set at the Top Seed Open in Kentucky.
But she recovered to prevail 4-6 6-4 6-1 in two hours and 15 minutes.
“I knew I could play a little bit better if I hung in,” Williams said.
Williams will next play her sister Venus Williams – another former world number one – after her straightforward 6-3 6-2 win over Victoria Azarenka.
Serena’s last competitive action was in the Fed Cup tie against Latvia in February and it showed in the early stages as she surrendered the first set and offered up breakpoints in the first game of the second. (BBC)