LEXINGTON, KY, USA - Former World No.1 Serena Williams made a triumphant return to competitive tennis on Tuesday, surviving a stern test from countrywoman Bernarda Pera to advance, 4-6, 6-4, 6-1 at the inaugural Top Seed Open presented by Bluegrass Orthopaedics.

"It was a really calm atmosphere, really chill," Serena said after the match. "I can't say I disliked it. It was different; I've been through so many things in my career. I think I won today because I was calm for once, so that was really helpful."

Williams was playing her first match since helping lead the United States to a Fed Cup victory over Latvia, and her first tournament since the Australian Open in January, with the WTA tour having been shut down due to the COVID-19 pandemic in early March.

"I haven't played, like a lot of players have managed to play little things against other players. I've only been training, so I was missing shots, but getting back into the swing of things at the same time."

Five points from defeat in the second set, the 23-time Grand Slam champion, who has been in hot pursuit of Margaret Court's all-time record, showed off her inimitable fighting spirit to dispatch Pera after two hours and 16 minutes on Center Court.

"I just knew I needed to do better. I knew I could, and she hit so many winners, low to the court. I had to get used to her game a little bit, because she played really well."

Born in Croatia, the 25-year-old Pera cracked the Top 100 for the first time in 2018 - the year she reached the third round of the Australian Open and scored a first career Top 10 win over Johanna Konta en route.

2020 Lexington highlights: Williams passes Pera test

Her best WTA results of 2019 all came on clay, making three semifinals at the J&T Banka Prague Open, the Ladies Open Lausanne, and the Baltic Open in Juurmala, where she knocked out former French Open champion Jelena Ostapenko in the first round.

Playing the 23-time Grand Slam champion for the first time, the lefty showed little fear in the opening set, nabbing a break in the fifth game and saving two break points on her own serve to maintain her lead. She put away her first set point opportunity with a heavy forehand winner.

"I didn't know how I was going to feel or how I was going to do, but I really didn't hate the atmosphere. Being in New York will be a little different because of the massive stadium, but the solo court kind of reminds me of my junior days, so there was something kind of nostalgic about that."

Williams gamely dug out of a 0-40 deficit to start the second set, and was soon in front 3-1 before Pera leveled things up. Down 0-40 again at four games apiece, she saved four break points that would have helped her countrywoman serve for the match.

Looking to force a decider, the top seed earned a pair of set points on the Pera serve, converting the second with a deep forehand strike that forced an error.

"I was pleased with how competitive I was out there, staying in the moment and not getting down on myself. I don't know how much I need to work on because I'm playing unbelievably in practice! I know I'm going to get better with each match, and I'm ok with that because today was nothing compared to how I'm practicing. I just need more rhythm, more time to be out there playing the match."

Returning more confidently to start the third, Williams took another 3-1 lead and this time made no mistake, saving two break points in the following game to consolidate.

Down 40-0 after the changeover, the former World No.1 roared through the final nine points to race over the finish line and book an exciting second round clash against either former World No.1 Victoria Azarenka or five-time Wimbledon champion and elder sister Venus, who face off later in the afternoon.