The 18-year-old rising star is one of 12 Australians scheduled to play on Monday after a rain-disrupted opening day at Melbourne Park.
Drawing the seventh-seeded American, Joint said she was going into the first-round clash with the attitude that she had "nothing to lose".
"I like being the underdog in matches," the Australian wildcard told reporters.
"Just go out, have no pressure, see what I can do."
Joint is knocking on the door of the top 100 for the first time following a run to the semi-finals in Hobart, her best result at a WTA 250 event.
Despite her hot start to 2025, the world No.105 retains modest goals for the rest of the year.
"I'd like to get inside the top 100," she said.
"I'd like to play all of the slams. Just improve my game mentally, improve all aspects of it."
Jessica Pegula says Joint will have the benefit of being an unknown quantity in their match. (Matt Turner/AAP PHOTOS)
Australian women's tennis has not reached the same dizzy highs since the days of Ash Barty, who suddenly called time on her triple grand slam-winning career in 2022.
Joint switched allegiance from the United States to Australia in early 2023 and said she had enjoyed the local crowd treatment so far.
"It's been amazing," she said.
"I mean, when I played the first time, they really made me feel like I was always representing Australia."
Pegula is wary of the Australian youngster, coming fresh off Saturday night's three-set loss to countrywoman Maddison Keys in the Adelaide International final.
"It's going to be a really tough match," she said.
"Only having a day here as well to kind of get used to the conditions.
"Of course, it rained too, so I wasn't able to hit outside. It's always tough playing a player where you don't have a lot of familiarity there."
Nick Kyrgios headlines the other Australians in action on Monday, making his grand slam comeback after more than two years on the sidelines, playing Britain's Jacob Fearnley.
His doubles partner Thanasi Kokkinakis, 27th seed Jordan Thompson and three-time grand slam quarter-finalist Ajla Tomljanovic will also get their campaigns under way after Sunday's six-and-a-half-hour rain delay.
AUSSIES IN ACTION ON DAY TWO OF THE AUSTRALIAN OPEN (PREFIX DENOTES SEEDING):
Men's singles, first round:
27-Jordan Thompson v Dominik Koepfer (GER)
Nick Kyrgios v Jacob Fearnley (GBR)
Thanasi Kokkinakis v Roman Safiullin (RUS)
Chris O'Connell v 12-Tommy Paul (USA)
James Duckworth v Dominic Stricker (SUI)
James McCabe v Martin Landaluce (ESP)
Tristan Schoolkate v Taro Daniel (JPN)
Aleksandar Vukic v Damir Dzumhur (BIH)
Women's singles, first round:
Ajla Tomljanovic v Ashlyn Krueger (USA)
Maya Joint v 7-Jessica Pegula (USA)
Talia Gibson v Zeynep Sonmez (TUR)
Destanee Aiava v Greet Minnen (BEL)
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