Both players have overpowered their opponents so far in this tournament. Barthel was merciless in dispatching Swede Johanna Larson 6-1 6-2 in just 44 minutes yesterday.
"She serves really hard and has really hard ground strokes and she hasn't really had any trouble getting into the semis here," Wickmayer said.
"She must be playing well and she played really well at the beginning of last year. I played her in the final at Hobart and lost pretty bad there. I am going to have to be ready for some big shots."
The rangy Wickmayer has been dishing out plenty of big shots of her own. Yesterday, she was largely untroubled in subduing countrywoman Kirsten Flipkens 6-3 6-4 in a match that featured a cluster of short rain delays and a contentious over-rule from the chair umpire on match point.
Replays backed up the distraught Flipkens' view - and that of the line judge - that the ball was well wide.
It is unlikely the blown call would have changed the result, but Flipkens had every right to feel aggrieved and protested at length before departing centre court.
Top seed Agnieszka Radwanska also breezed through, defeating Russian Elena Vesnina 6-3 6-3 in a match interrupted by a 90-minute rain delay. That match was also blighted by a number of poor line calls, with Vesnina the victim twice in a crucial service game.
The quality of the officiating was an issue for the players, Radwanska confirmed. "It is a really good tournament. Everything is perfect - but one thing is missing," she said.
The classy Pole will take on American Jamie Hampton, who defeated Dutchwoman Kiki Bertens 6-1 6-7 (5) 6-2 last night.
Results
Quarter-finals
3-Yanina Wickmayer (BEL) bt Kirsten Flipkens (BEL) 6-3 6-4
8-Mona Barthel (GER) bt Johanna Larsson (SWE) 6-2 6-1
1-Agnieszka Radwanska (POL) bt Elena Vesnina (RUS) 6-2 6-3
Jamie Hampton (USA) bt Kiki Bertens (NED) 6-1 6-7 (5) 6-2
Today
From 12 noon
Semifinals
3-Wickmayer v 8-Barthel
1-Radwanska v Hampton
