Serena Williams showed she has made a full recovery from recent health issues by beating Angelique Kerber 7-6 6-3 in the final of the Stanford Classic on Sunday.

Williams, playing in her first tournament since being forced to retire from a Wimbledon doubles match because of a viral infection, took the Stanford crown for a third time and won her fourth title overall this season.

Her return to fitness has come at just the right time with the US Open set to start on August 25.

“I have a lot of confidence going but every week is a new week and hopefully I can just try to improve,” Williams, who also took the title in 2011 and 2012, told reporters.

Her latest victory was far from easy as Williams had her service broken twice in the opening set and fell behind 5-1.

The 17-times grand slam champion rallied to tie the score and eventually dominate the tiebreaker 7-1.

“I blinked my eye and I was down 1-5 and Angelique was playing so well,” the 32-year-old said.

“I tried to relax and just think about making my shots.”

Williams claimed a 2-0 lead in the second set and held off her German opponent the rest of the way. She fired six aces and did not face a break point in the final set.

Kerber was looking for her first singles crown of the season but instead lost her fourth final of 2014.

“I gave everything I could,” Kerber said.

“When she was down she started hitting the ball better I think. It’s a special thing that she has.”

Meanwhile, Milos Raonic won the first all-Canadian final of the professional era when he beat Vasek Pospisil 6-1 6-4 in the final of the Citi Open in Washington.

Raonic took barely an hour to dispose of Pospisil at the William HG Fitzgerald Centre, breaking serve three times in the first set.

The second set was a tighter battle as Pospisil raised his game before Raonic delivered the knockout blow in the 10th game for his sixth ATP title, his first of the year.

Raonic, 23, playing his first event since making the Wimbledon semis, has risen from seventh to sixth in the ATP rankings.