SAN JOSE, CA, USA - The highest-seeded player left at the Mubadala Silicon Valley Classic stayed alive on Thursday night.

In just under two hours, No.3 seed Venus Williams held off a game effort from Great Britain's Heather Watson to reach the quarterfinals, 6-4, 4-6, 6-0.

The tournament lost both No.1 seed Garbiñe Muguruza and No.2 seed Madison Keys to injury this week, with each woman forced to withdraw before their second round matches.

Taking the court for the first time this week, the American did not join them on the sidelines - despite being given a scare - thanks to a flawless third set.

"It was a tough match and she played incredible. There were times where I had no answers. This court here is amazing and I'll be back tomorrow," Williams said on-court after the match.

"[I just wanted to] control the points and enjoy the battle, just get out there and try to do what I know that I can. It worked out, thankfully."

The seven-time major champion broke three times, dropped just four points on serve, and was never broken after losing serve a total of three times in the first two sets.

The American's winning debut on the campus of San Jose State University comes in her 14th appearance at the event, having reached eight finals in this calendar week overall in her career.

Williams is a two-time champion, lifting the title in 2000 and 2002. In addition, finished as the runner-up in 1998, 1999, 2004, 2005, 2009 and 2016.

To score victory on Thursday night, the No.3 seed struck 24 winners and went 6-for-12 on break points. The American's returning increased in accuracy as the match progressed, affording her opportunities in the Brit's service games despite Watson landing 70 percent of her first serves.

"I want my game to improve this whole tournament, so I wanted to have that mentality," she said. 

"The first match is always a test. In a lot of ways, I was kind of happy that it went to the third, because I was forced to lift my game even more and really try to get on my best tennis. I have to be able to be ready for the best tennis at all times through the match, no matter who I'm playing."

The World No.14 was first to drop serve in the match as Watson moved ahead in the third game of the first set, but she quickly restored parity with an immediate break.

The two players went with serve from there, with neither facing break point, until the American sealed the opener by winning the last three points in the 10th game.

The second set began in identical fashion, but Watson held on to her break until the eight game of the middle set. Though the 38-year-old pulled even with her third break of the match, she wobbled again on serve from 30-15 up to allow the World No.133 an opportunity to serve for the set.

Watson won her first set in four played against the American champion as she sent the match the distance, but that proved to be the last game she'd win in the match. 

Williams will next face Greece's Maria Sakkari, who dropped just one game in a rout of No.8 seed Timea Babos. The two have played twice previously at Grand Slams in the past two years, with the American winning encounters at Wimbledon in 2016 and at the US Open last year.

"I have to play my best again. I know that it's never easy, and I'll have to earn it, just like tonight," she said. "So, I'll be doing the same thing tomorrow. I've played her and definitely seen her...I knid of know what to expect, so we'll see."