Mladenovic, who had taken out No.1 seed Lucie Safarova earlier in the tournament, came out firing, breaking at love in the third game of the match en route to an early 3-1 lead. But Nara, who also took out one of the favorites earlier in the week - No.7 seed Madison Keys - went into overdrive from there, winning 11 of the next 12 games to cruise through in just an hour and 14 minutes, 6-3, 6-1.
Next up for Nara will be Erakovic, who ended the run of another WTA Rising Star, Bojana Jovanovski, reeling off six straight games from 3-4 in the first set to build a 6-4, 3-0 lead and never really looking back, eventually making it past the hard-hitting young Serb in an hour and 20 minutes, 6-4, 6-4.
"Overall it was a really tough match," Erakovic said. "It was really humid out there and we did a lot of running, and Bojana is a very solid girl - she hits a big ball and it can be really difficult for me to dictate. So I just had to keep fighting out there and take chances whenever the chances came."
Nara and Erakovic are tied in their head-to-head, 1-1, though they haven't played in four years.
The other semifinal will feature two of the four best Russians on the WTA - Ekaterina Makarova and Svetlana Kuznetsova. The No.6-seeded Kuznetsova was the first to advance though she didn't even have to hit a single ball, advancing via walkover when Vania King withdrew due to a right hip injury.
In the highest-profile quarterfinal match-up of the day, the No.2-seeded Makarova edged No.5-seeded Anastasia Pavlyuchenkova in a one-hour, 47-minute two-setter, 7-6(3), 6-3. Pavlyuchenkova had her chances in the first set - she was two points from winning the set with Makarova serving at 4-5, 30-all, and she was also up 2-0 in the tie-break. But Makarova snuck it out and cruised from there.
Kuznetsova leads Makarova in their head-to-head, 3-1, which includes a 2-0 record on hardcourts.
They are two of the four highest-ranked Russians on the WTA Rankings at the moment. Maria Sharapova is at No.6, then Makarova at No.20, Pavlyuchenkova at No.24 and Kuznetsova at No.26.