The pair's three previous meetings all went to three sets and this one did the same, Halep taking the first set, 6-4, and Jankovic retaliating in the second set, 6-2. The first game of the third set turned out to be a huge turning point - a marathon five-deuce game that eventually went to Halep swung the match completely, as the No.11-seeded Romanian steamrolled to beat the No.8-seeded Serb, 64 26 60.
"She played really well in the second set," Halep said after the match. "I was a little bit tired after the first set - my energy was very down - but I was ready to play the third set. I was just telling myself I had nothing to lose - it was my chance to fight for every point and for the match, and for my dream.
"It was my dream before starting this year to play the quarterfinals of a Grand Slam."
She is also likely going to break into the Top 10 after this tournament - if that happens she would be the third Romanian ever to break into the elite, after Virginia Ruzici and the aforementioned Spirlea.
"I hope," Halep said of the Top 10. "I'm really happy to hear that, but I have to focus on my next round, because a Grand Slam is a Grand Slam. I'm not focused on my ranking. I want to enjoy every match."
Halep had an absolute breakthrough second half of the 2013 season - from May through the end of the year she won 43 of 51 matches, her first six WTA titles and rocketed from No.64 all the way to No.11. Her start to 2014 was shaky - she lost her opening match in Sydney - but she seems back on track.
"I started to play well in Madrid," Halep said. "Mr. Tiriac gave me a wildcard and helped me a lot. I lost first round but I played three hours, and after that I felt I was playing at a very good level. I beat Radwanska in Rome and after that I had confidence I could beat top players and be in the top level."
Jankovic may not have won but she tried to look on the bright side afterwards in her presser.
"What can I say? It's obviously disappointing when you lose, especially when it's a tough match. These last three rounds I played, I was fighting a lot, because I wasn't playing my best tennis. But I was in there. Today I lost a few points here and there - if I was a little bit smarter and fitter at times I would have done much better. But it didn't go my way. But all credit to her, she played really well today.
"Overall it's okay. It could have been better. I thought I was going to go further, but that's life."