Kicking off the opening day action on Cancha Central, the Frenchwoman needed just an hour and fifteen minutes to complete the 6-2, 6-3 victory.
"It felt great to play the first match on Central," Mladenovic said after the victory. "I was actually really surprised at the schedule, you know, to open up the tournament on the center court.
"It was difficult for me, too, because I arrived just two days ago from Dubai. I'm still a bit jetlagged and it's totally different conditions here, but I'm just very happy with the win."
Mladenovic got off to a quick start against the No.91-ranked American, jumping ahead to a 3-0 lead in both sets. Mladenovic played aggressive, positive tennis to keep Lepchenko out of the rallies, hitting a serve out wide and following it up with a booming forehand. She closed out the set with a second break to the Lepchenko serve.
? WTA (@WTA) February 27, 2017
But the American stood her ground heading into the second, mixing up her game plan to play more aggressively and earn a break back and level the score at 3-3.
Mladenovic stayed positive, and peppered her game with dropshots to grab another break and serve out the match, sealing it with another ace out wide - her fifth ace of the match.
"I was trying to stay tough in my head, just trying to work for every single point, every game. I was just trying to go for it, and Varvara is a tough player as well. Very happy with this first win."
? WTA (@WTA) February 28, 2017
Also through in Acapulco, No.8 Andrea Petkovic faced a tough battle against American qualifier Jamie Loeb, needing to come back from a set down in her 2-6, 6-1, 6-3 victory.
"I've been here for a week already so I've been practicing for a long time," Petkovic said. "I don't remember the last time I waited this long for a match. So at the beginning I was a bit tight, because also she had been through qualifying here"
"She was playing really fast, and I needed some time to get used to it. In the second and third set - after some rough patches - I think it was pretty good."
Joining them in the second round will be Shelby Rogers, who moved past her American compatriot Louisa Chirico 6-2, 6-2, and Pauline Parmentier who survived a rollercoaster against Nicole Gibbs to advance 7-5, 6-7(6), 6-2.