Serena got her groove back and just in the nick of time. After an inauspicious start in which the unforced errors drastically outnumbered the winners, the twenty-three-time grand slam champion hit the reset button and dispatched Karolina Pliskova, the #8 seed in straight sets.

Williams, the six-time US Open champion, was sluggish and mis-firing during most of the first set. Pliskova, the 2016 US Open finalist, defeated Williams 6-2, 7-6 in the semis that year so was aware how critical it was to announce her presence and secure the first set.

Initially, it appeared that history would repeat itself. While both held to 30 in their opening service games, Williams came under significant pressure in the third game when she donated a double fault to face break point. Despite hitting two aces, Williams repeatedly missed on the first serve providing Pliskova numerous opportunities to take control early in the points.

Following three deuces and three break points, Pliskova converted when another Williams’ backhand found the net.

Pliskova, serving at 2-1, held to love as her opponent’s unforced errors continued to mount. Williams was in danger of going down a double break as her serve and formidable groundstrokes appeared to be missing in action. Although she faced four deuces and three break points, the soon to be thirty-seven-year-old held for 2-3 as her opponent repeatedly missed off the ground.

Pliskova, failing to capitalize on Serena’s erratic play to go up a second break, faced double break point in her next service game but managed to hold as Serena continued to overcook her groundstrokes.

Pliskova, once known for leading the tour in aces over multiple seasons, did not take full advantage of her opponent’s second serves. Serena held to 15 for 3-4 and would break in the following game when Pliskova netted two backhands on consecutive points.

The crowd in Arthur Ashe stadium went from dazed and confused to enthused and elated. Level at four games apiece, Serena held to 15 with a huge serve out wide.

Pliskova served to stay in the set and despite a 40-0 lead, found herself facing multiple break points as she played too tentatively while Williams found her range off the ground. Pliskova was on her heels as winners flew off Serena’s racquet and dropped serve to lose the set 6-4 as another backhand found the net.

Neither, unfortunately, played well at the same time. Pliskova, incredulously, did not serve a single ace in the first set and won less than 57% on first and second serve points. She committed 12 unforced errors to 5 winners.

Williams struck four aces and while she won 62% on first serve points, she barely was above 50% on second serve points. She was keenly aware that her opponent had let her off the hook and she would need to radically up the ante if she was to win in straight sets. She also would have to severely minimize the unforced errors as she committed 22 to just 17 winners.

Serena served first in the second and despite throwing in a double fault, held to 30. Pliskova faced triple break point in her opening service game and was broken as the forehand errors continued to multiply.

Serena struck two aces in her next service game and held to take a 3-0 lead. Pliskova dropped serve for a second time as she continued to misfire off the ground while her opponent continued to hit winners.

At this juncture in the match, it looked like Williams would take the second set at love but suddenly, her first serve deserted her. Although she hit an ace to save one break point, Serena dropped serve with her second double fault of the game.

Pliskova seemed emboldened as she held to love with an ace for 2-4. Serena, serving with new balls, faced triple break point as her backhand repeatedly sailed long. Despite facing four break points, she remained steadfast as she unloaded on serve, striking two aces and a cross-court backhand winner to hold.

Serving at 2-5, this was a must hold for Pliskova. She played much more aggressively, executing two impressive stab backhand volley winners, a cross-court forehand winner and two consecutive aces to hold for 3-5.

Serena, serving for the match and a spot in the semifinals, wasted no time, hitting three aces and an overhead smash winner to hold at love. In the second set, she hit five more aces and hit more winners than errors.

Serena will need to play markedly better from the start against her next opponent, the creative and versatile Latvian, Anastasija Sevastova. This will be their third meeting, Serena having won the previous two.

They last played this past spring in Indian Wells and it was a tight two-setter. Sevastova is competing with a great deal of confidence especially after dismantling the defending US Open champion Sloane Stephens, in straight sets in the previous round.