Serena Williams began her US Open quarter-final tentatively. Her shots lacked their usual sting, her attitude its usual conviction.
She was facing the last player she lost to at Flushing Meadows, and perhaps that was the problem. After just 20 minutes this afternoon, Williams was in danger of trailing by two service breaks.
Not much later, the outcome was no longer in doubt, because the 23-time Grand Slam champion suddenly was in complete control.
Williams put aside some early shakiness and an early deficit, turning things around with an eight-game run en route to a 6-4, 6-3 victory over No. 8 seed Karolina Pliskova for a spot in the semifinals.
"I thought, 'Oh, I've got to try harder,'" said Williams, who wound up with 22 of her 30 unforced errors in the first set.
By the end, Williams compiled a 13-3 edge in aces, and 35-12 in total winners.
Pliskova is a big server and hitter in her own right, someone who briefly spent time at No. 1 in the WTA rankings and was the runner-up at the US Open in 2016, when she beat Williams in the semi-finals.
The 36-year-old American did not compete in New York a year ago, because she gave birth to her daughter during the tournament.
Go back to 2015, and that was another semifinal departure for Williams, whose bid for a calendar-year Grand Slam was shockingly ended by Roberta Vinci.
"Well, I want to just be able to get past the semis here. It's been a few, couple, rough semis for me," Williams said. "But regardless, this has been a great road."
This time, Williams' semifinal opponent will be No. 19 seed Anastasija Sevastova of Latvia, who surprisingly beat defending champion Sloane Stephens 6-2, 6-3 earlier today.
Sevastova, who retired in 2013 because of injuries and returned nearly two years later, advanced to her first Slam semifinal.
"Still long way to go, I think," she said.
Especially considering that the next step will come against Williams, who's heading into her 36th semi at a major, 12th at Flushing Meadows.