No.1 seed Serena Williams survived a major scare before emerging victorious over Bernarda Pera in the first round of the WTA tournament in Lexington.
The 4-6 6-4 6-1 win sets up a second-round bout against Venus Williams, who brushed aside fellow former world No.1 Victoria Azarenka for the loss of just five games.
Across the Atlantic in Prague, world No.2 Simona Halep also endured a tough opener, stretched to a final-set tiebreak against Polona Hercog before triumphing 6-1 1-6 7-6(3).
Serena found herself up against an inspired opponent in Pera, the world No.60 who frequently used her powerful forehand to devastating effect.
Pera earned 13 break points throughout the match, yet was able to win just two.
Four of those break point opportunities came in the ninth game of the second set, which, if she had converted, would have given her the chance to serve for the match.
Yet from 0-40 down in that game, Williams erased two of them with winners, held serve, and dropped just one more game for the entire match.
"I think I won today because I was calm, for once in my career, and I think that was really helpful,” said Williams, who believed that calmness stemmed from the crowd-less atmosphere at the event.
"She hit so many winners, and (kept the ball) so low ... she played really well.
"I don't know if I need to work on anything. I'm playing unbelievable in practice. So I actually am calm.
“I know I'm going to get better with each match and I'm OK with that, because I know that compared to what (level) I'm practising, that was nothing. I know it's gonna come.”
Serena will play Venus for the 31st time when the sisters face off in Lexington.
Serena leads the head-to-head series 18-12, having won nine of their past 11 meetings, and their most recent encounter 6-1 6-2 in the third round of the 2018 US Open.
Also progressing to the second round in Lexington was teen star Coco Gauff, who beat qualifier Caroline Dolehide 7-5 7-5.
The victory sets up a meeting with No.2 seed Aryna Sabalenka, who a day earlier got past Madison Brengle in three sets.
Halep survives a battle
In Prague, Halep led Hercog by a set and a break but ultimately required seven match points to see off her Slovenian opponent.
Playing her first match since winning the WTA Dubai title in February, Halep let leads of 3-1 and 5-3 in the final set slip before eventually closing out the match in two-and-a-half hours.
"I didn't get upset, which I'm very proud of. I just fought, I knew that if I had those chances (match points) I would have another one,” said Halep, who next faces Czech wildcard Barbora Krejcikova for a place in the quarterfinals.
"I felt tension in my back after the first set, even though it was short and I played well. After the second set, I felt tired.
“But I knew she was in the same position so I just had to stick to the plan and fight - the fighting helped me to win the match.”
Joining Halep in the second round in Prague were second seed Petra Martic and No.3 seed Elise Mertens, with Mertens requiring three sets to get past Italy’s Jasmine Paolini.