Before we begin, or even after we're done, click on the video above to watch highlights from Petkovic against Bouchard in the Charleston semifinals this year - could that be our final match-up here?
Now, here are 10 Things To Know about Halep and Petkovic's quarterfinals and the looming semi...
1) Petkovic only hit four second serves in her quarterfinal match.
Petkovic went into her match against Sara Errani with the odds stacked against her: lower-ranked, never won a set in three previous Grand Slam quarterfinals, lost their last head-to-head meeting in straight sets. But she was dialed in this time, serving up a storm - she hit 41 of 45 first serves in (a 91% first serve percentage). She would cruise past Errani in 63 minutes, 6-2, 6-2 (read more here).
2) Halep took a little bit longer than Petkovic but got to the same destination.
Halep didn't have a big ol' 91% on her stats sheet but she was pretty amazing herself against Svetlana Kuznetsova, blasting 18 winners to win in an hour and 19 minutes, 6-2, 6-2 (read more here).
3) Both Halep and Petkovic are in their first Grand Slam semifinals now.
Before this tournament, Halep's best Grand Slam result was a quarterfinal at the Australian Open this year (falling to Dominika Cibulkova), and Petkovic's best results were three quarterfinals in 2011, at the Australian Open (falling to Li Na), the French Open (falling to Maria Sharapova) and the US Open (falling to Caroline Wozniacki). Neither player won a set in any of those previous quarterfinals.
4) When was the last time a Grand Slam semifinal featured two first-timers?
The last time a Grand Slam semifinal featured two first-time Grand Slam semifinalists was at the 2009 US Open, when Caroline Wozniacki faced Yanina Wickmayer. Can you remember the last time before that that it happened? Hint - it was two future World No.1s, right here... find the answer here.
5) Halep will rise to No.3 if she reaches the final.
In March, Halep rose from No.7 to No.5, becoming the new highest-ranked Romanian in WTA history. She then raised the bar to No.4 just before Roland Garros, and with one more win, she'll go one higher.
6) Petkovic will have her own ranking rise after this tournament.
Petkovic is projected to rise from No.27 to No.20 by virtue of reaching the semifinals, her first time in the Top 20 since August 2012. The former No.9 could go as high as No.11 by winning the title.
7) Petkovic is the third post-Graf German to reach a Grand Slam semifinal.
Since Steffi Graf's last Grand Slam semifinal at Wimbledon in 1999, only three Germans have reached Grand Slam semifinals - Sabine Lisicki (one semifinal, one final), Angelique Kerber (two semifinals) and now Petkovic (one semifinal). Graf reached the semifinals or better an insane 37 times in her career.
8) Halep is 2-1 against Petkovic, and 2-0 in the last year.
Petkovic beat Halep at an ITF Women's Circuit event back in 2009, but their last two meetings both came in 2013, with Halep winning both in straight sets. Take a closer look at their head-to-head here.
9) There's a 10 Things To Know about the other semifinal.
Just in case you missed it, click here for 10 Things To Know about Sharapova Vs Bouchard.
10) The semifinals start at 3pm Paris time Thursday - check your local listings!