Seven-time Wimbledon singles champion Serena Williams reached the quarter-finals at SW19 with a dominant display against Spain's Carla Suarez Navarro.

The American 11th seed, 37, raced to a 6-2 6-2 victory against the 30-year-old world number 31.

Williams will play compatriot Alison Riske in the last eight after she upset world number one Ashleigh Barty.

In another unexpected result, Karolina Muchova beat third seed Karolina Pliskova 4-6 7-5 13-11.

The all-Czech encounter was a game away from becoming the first Wimbledon match decided by the new rule which sees a tie-break played if it reaches 12-12 in the final set.

But world number 68 Muchova, who has never reached a Grand Slam quarter-final before, hit a forehand winner to break at 12-11 up and claim victory after three hours and 17 minutes.

The 22-year-old will face Ukrainian eighth seed Elina Svitolina next, who moved into the last eight with a 6-4 6-2 win against Petra Martic.

Williams is also in the second round of the mixed doubles with Britain's Andy Murray and said she was happy to have more playing time at the All England Club.

"I have more matches this week than in the past five months, but it is good," she explained.

"I know I can play and now that I feel better physically I almost feel a relief. I still want it or I wouldn't be here."

Williams took control from the outset, breaking Suarez Navarro's serve in the first game then breaking again to go 5-2 up.

But shortly before that Williams, who played in her first Grand Slam in 1998, had to be reminded of the rules by the umpire as she reached over the net to hit a volley.

The 23-time major winner told the umpire "I thought it was allowed" after the point was overruled, but was ultimately undisturbed as she claimed the first set in 31 minutes.

Williams made an equally commanding start to the second set as she broke Suarez Navarro in her first two service games, but the four-time Olympic champion then dipped momentarily as she lost her serve to love.

Suarez Navarro has never won more than three games in a set against the American though, and Williams ensured that record continued as she broke for a third time then held serve to close out the match in one hour and four minutes.

Elsewhere, Belgian 24th seed Elise Mertens served for the match against the Czech Republic's Barbora Strycova but was eventually beaten 4-6 7-5 6-2.

The world number 54 will play Britain's Johanna Konta or Petra Kvitova next.

China's Zhang Shuai held off Ukrainian 19-year-old Dayana Yastremska 6-4 1-6 6-2 and will now play Simona Halep, who ended 15-year-old Coco Gauff's run with a 6-3 6-3 victory.

Analysis

American former world number six Chanda Rubin on BBC TV

This was just a classic Serena Williams performance. Everything was firing and on point.

Carla Suarez Navarro is an opponent she has never really had trouble with. Williams broke her in the first game and she never looked back.

She did not have enough against Williams' power, serving and movement.