But the four-time major winner broke in the next game to book her spot in the second round against France’s Elsa Jacquemot.
“I’d say that for me it’s not always easy in the first rounds,” Sabalenka said.
“And then, as I get further in the tournament, as I get more comfortable, my level becomes better.”
Following a wet and cold Italian Open earlier in May and similar conditions during the practice week at Roland Garros, the big-hitting 28-year-old said the scorching conditions played somewhat in her favour.
“I’d say that it was a bit warm,” she joked.
“Especially compared to the first days when I first got here, it was like 14C, like, freezing.”
“Now it’s boiling, and balls are flying, everything is much faster. But physically I feel strong, so I feel like it can benefit me.”
Women’s defending champion Coco Gauff made short work of fellow American Taylor Townsend, kicking off her tournament with a clinical 6-4, 6-0 performance.
The fourth seed joked the heat was “nothing” as she grew up in Florida, but added: “Honestly, I felt more bad for the fans. Dang, you’re watching in the heat, and I hoped no one passed out. So I’m glad I finished quickly.”
Felix Auger-Aliassime claimed a fifth-set tie-break to move into the Round of 64 as the Canadian narrowly avoided coming undone against Germany’s Daniel Altmaier.
Russian sixth seed Daniil Medvedev was not so fortunate, however, going down in five sets to Australian wildcard Adam Walton.