An out-of-sorts Muguruza battled with the heat, her health and a fearless opponent before eventually triumphing, 2-6, 6-0, 6-3, in a fraction under two hours.
It has been a bleak summer for the Spaniard, who, until a timely run in Cincinnati, had struggled to cobble wins together since her breakthrough at Roland Garros. Against a player making her Grand Slam debut, these problems were laid bare in an opening set containing 17 unforced errors.
"Well, it happens more in the Grand Slams at the beginning of the rounds because there's a lot of people and sometimes you don't know the opponents," Muguruza said. "Today was this sort of case.
"I went to the court and I didn't really know the opponent. You play and you do your stuff. You kind of see a little bit during the match how she plays, but you cannot know anything before."
Muguruza could overthrow Serena Williams at the top of the rankings with a deep run this fortnight, and in the second set she illustrated her undoubted class, reeling in the unforced errors to level the match up in emphatic fashion.
A contest of wildly fluctuating fortunes ultimately hinged on a couple of points; locked at 3-3 in the decider, Muguruza fended off a break point with a forehand winner before striking herself the following game as the World No.137's spirited challenge finally wilted.
Flushing Meadows has not been the happiest of hunting grounds for Muguruza, who has never reached the third round in three previous visits. Standing between her and this juncture will be Anastasija Sevastova, a 6-3, 6-3 winner over Anna Karolina Schmiedlova.
In spite of her struggles, the World No.3 is keen to embrace the tournament's unique challenges: "There's more movement, more noise, more stuff. But it's well known also because of the environment and the crowd and the vibes that New York brings.
"I think it's also special to feel the energy from all these people. They're watching you. Maybe it's not as quiet as Wimbledon, but I enjoy it a lot."
? ESPNTennis (@ESPNTennis) August 29, 2016