On a rain-interrupted day in the Hungarian capital, conditions were heavy on court and Errani took a few games to find her rhythm. However, once she did, there was no stopping the top seed; from 3-1 down in the opening set, she rattled off 11 of the next 12 games to humble her fellow Italian, 64 60.
"It's difficult to play against someone you know well," Errani said. "There was more tension than in a usual match and I think that showed in the first set, which was not too good. I got better in the second set and in the end I was playing well."
Meeting her in the last four will be Anna Tatishvili, who overcame a tenacious Aleksandra Wozniak in three absorbing sets on Court Asboth Jozsef. In what was undoubtedly the match of the tournament so far, Wozniak fought back from 5-1 down in both the second and third sets - saving a staggering eight set points and four match points in the process - only to come up fractionally short, as Tatishvili prevailed, 57 76(4) 64.
Meanwhile, the other semifinal will pit Elena Vesnina against No.5 seed Marina Erakovic. Vesnina, who has dropped just five games in the opening two rounds, continued her serene progress on Day 4, seeing off both the weather and No.6 seed Petra Martic.
Prior to this week, Vesnina had won back-to-back matches only once this year and was understandably delighted after completing her 63 62 win. "I'm really happy to be in my first semifinal this year and finally I'm playing good and enjoying my tennis," Vesnina said.
"It was a strange beginning to match because we went on court and then it started raining so we went back to the locker room and then we came back!" she added. "Petra is a young, talented player and I knew I had to move her around. The score doesn't represent the match because it was actually really close and it could easily have been 63 62 to Petra."
Erakovic's quarterfinal with Barbora Zahlavova Strycova, on the other hand, was far more of a topsy-turvy affair. In another match punctuated by rain delays, neither player managed to stamp their authority on proceedings, however, after two one-sided sets it was Erakovic who held her nerve in an hour-long decider to progress, 62 16 64.
"The match was tricky," Erakovic said. "We both started pretty nervously and had to adapt to the circumstances in the first set when it was a bit rainy. After I lost my rhythm a little bit in the second set, I started to play more steady in the third and managed to adapt to her style and play more positively."