Felix Auger-Aliassime received a walkover into a Stuttgart Open final against Matteo Berrettini, while the Rosmalen Grass Court Championships semi-finals will not conclude until Sunday.
A lower back injury led to sixth seed Milos Raonic, who was taking part in his first tournament since the Miami Open in March, withdrawing from the all-Canadian final-four match in Germany.
"I'm very sorry and apologetic that I'm unable to compete. I was hoping for the best after my match yesterday," said 2016 Wimbledon finalist Raonic.
"I woke up this morning not feeling my best. I wanted to come out here and give it a try. And after looking at it very diligently with my team, and the way I was feeling with my back, I found it was not possible for me to compete without taking any greater risk."
@milosraonic: "It's hard for me to accept this situation but it is how it is.— Tennis TV (@TennisTV) June 15, 2019
"But I'm happy that Felix has an opportunity to win his first title, so I wish him all the best." #MercedesCup @felixtennis pic.twitter.com/ofKe9qtO9b
Berrettini faced his first two break points of the tournament but staved them off en route to a 6-4 7-5 victory over home hope Jan-Lennard Struff.
In Den Bosch, Borna Coric saved two match points but fell a mini-break behind in a third-set tie-break before his semi-final against Adrian Mannarino was interrupted by rain.
Jordan Thompson claimed an important break to move 7-5 5-3 up against Richard Gasquet but was facing a break point in game nine of the second set when play was suspended.
The players will conclude their matches on Sunday before the final is contested.