Elise Mertens won two three-set matches on Saturday to reach the final of the Samsung Open in Switzerland.
The number two seed was on court for almost five hours in total.
She began her afternoon with a 6-4 5-7 7-6(0) victory against Germany's Mona Barthel in the quarter-finals, recovering from a break down in the deciding set to win in two hours and 36 minutes.
Mertens then beat Belarusian qualifier Vera Lapko 6-1 4-6 6-4 in the semi-finals in just over two hours.
The Belgian was also down a break in the final set against Lapko but reeled off the last three games to squeeze out another victory.
She will face either home favourite Stefanie Voegele or Aryna Sabalenka in the final.
At the Claro Open Colsanitas in Bogota, 2012 champion Lara Arruabarrena reached her second consecutive final after breezing past Dalila Jakupovic.
It was the second match of the day for world number 141 Jakupovic, who had earlier produced an upset by winning a two-and-a-half hour battle against number two seed Magda Linette.
She could not hold on to the momentum, however, and fell 6-1 6-2 to fifth seed Arruabarrena after just 50 minutes on court.
The Spaniard will face Anna Karolina Schmiedlova in the championship match, after the Slovakian player dispatched number seven seed Ana Bogdan.
Reaching her first WTA final since July 2015, Schmiedlova found her form to see off Bodgan 6-3 6-2 in just under an hour and 30 minutes.
