Kanepi was the first to move through, taking out No.7 seed Varvara Lepchenko, 63 46 76(4). Kanepi seemed headed for a straight set win as she built a 63 30 lead, even holding a 30-15 lead in her next service game, but it wasn't over as Lepchenko fought back to take the second set, then built a 5-3 lead in the third; but there was one last momentum swing left as Kanepi clawed back to sneak it out.
"After the rain delay in the second set it was so cold and it was hard for me to play well - but she came back so strong, which is really impressive because of the conditions," Kanepi said after the match. "We had another break early in the third set, so I took a shower and kept myself warm, and I think both of us played well in that set. When it got to the tie-break I was just trying to hit the ball and wasn't worrying too much about who would win the match, because we both played a really good third set.
"In a third set tie-break you always need some luck, because both of you played well to get there."
Hampton followed Kanepi into the semifinals after another quarterfinal nail-biter, taking out the No.2 seed, Roberta Vinci, 57 63 75. Hampton ran off five games in a row from 75 32 down to push the match into a third set, then came from 4-2 down to take the decider. Vinci served for it at 5-4, too.
"I'm very happy with my win today," Hampton commented. "My opponent is Top 20 in the world and plays very, very tricky tennis, and she's very experienced as well. I actually felt the first set was a good set of tennis for me, so I just tried to keep my spirits up and stay positive as I was going into the second set. When I was down in the third I just hung in there, and I'm lucky that it went my way today."
Hampton's win over the World No.15 was her third Top 20 win, her first two coming last year, over a No.14-ranked Jelena Jankovic at Indian Wells and a No.15-ranked Kanepi at Tokyo [Pan Pacific].
Hampton is now through to her second WTA semifinal, having gone this far at Auckland earlier in the year before falling to Agnieszka Radwanska. That was an International-level event though, and now she's in her first Premier-level semifinal - and on a surface she may not have expected it on.
"To be honest, clay isn't my best surface," the American said. "But I've fought hard and gotten a lot of match play out there this week, and I'm excited about the result and the challenge tomorrow too."
Hampton beat Kanepi in their only previous meeting, the aforementioned Tokyo meeting from last year.
The other semifinal match will pit No.8 seed Peng Shuai against Romina Oprandi, both of whom won their quarterfinal matches on Thursday. Peng and Oprandi are tied in their head-to-head series, 1-1.
Both semifinals and the final are on the order of play in the Belgian capital on Saturday.