Serena Williams Beats Karolina Pliskova in Straight Sets to Reach US Open Semis

Serena Williams advanced to the semifinals of the 2018 U.S. Open on Tuesday, defeating No. 8 seed Karolina Pliskova 6-4, 6-3 at Arthur Ashe Stadium in Flushing, New York.

Williams has reached the U.S. Open semifinals in each of her last nine appearances dating back to 2008.

The 36-year-old won the first set despite not playing her best. She committed 22 unforced errors, which equaled the number of unforced errors she made in her three-set win over Kaia Kanepi in the fourth round.

Pliskova led 3-1 to open the match and had three break-point opportunities in the fifth game. Williams held, though, and reeled off wins in five of the next six games.

As the Wall Street Journal's Tom Perrotta tweeted, the first set highlighted the way Williams' performance can change in a matter of moments:

Williams' hold in the fifth game may have been the turning point because the tide turned in her favor after that. She looked more dialed in, and her footwork was far sharper, allowing her to better dictate points with her groundstrokes.

Pliskova defended well to start the match, but she was largely powerless to prevent the onslaught once Williams got going:

The growing gulf between Williams and Pliskova was evident in the second set as Williams seized a 4-0 lead:

Pliskova made things interesting by winning two straight games and pushing Williams to 40-0 in the seventh game. She had four break-point opportunities, yet couldn't capitalize as Williams held serve to go ahead 5-2, making her victory all but inevitable.

Williams notched nine aces and 18 winners in the second set, while her unforced errors tally fell to eight. Beyond her stumble midway through the set, she was flawless.

The six-time U.S. Open champion will meet No. 19 seed Anastasija Sevastova in the semifinals Thursday. Sevastova is coming off a 6-2, 6-3 victory over defending champion Sloane Stephens. This will be the first time Williams and Sevastova have faced off at a WTA event.

Prior to upsetting Stephens, Sevastova toppled No. 7 seed Elina Svitolina, so she shouldn't be taken lightly.

The opening set will likely decide the outcome. The New York Times' Christopher Clarey noted Williams is unbeaten since March 2016 when she wins the first set. If Williams takes control early, then it could be game over for Sevastova.