Dubai - Angelique Kerber lost the chance to return to the top of the WTA rankings, after losing 6-3, 7-6 (7/3) to Elina Svitolina on Friday in the Dubai Tennis Championships semi-finals.
Had Kerber won the tournament, she would have retaken the world number one spot she held after winning the US Open in September, until Serena Williams wrestled it back in claiming Australian Open glory last month.
But Kerber, winner of two Grand Slams in 2016, fell victim to back problems during her match with Svitolina, who has now won her last three meetings with the 29-year-old German.
The top seed produced eight double-faults and left the court for medical treatment when a set and a break down.
Her return produced some momentarily inspiring tennis, with two bouts of light rain adding to complications.
It finally took a winning second-set tiebreaker from Svitolina to end the drama, sending the challenger into a Saturday title showdown against Caroline Wozniacki, who reached her second final in as many weeks, beating Anastasija Sevastova 6-3, 6-4.
Denmark's former world number one, currently 15th, took just 90 minutes to beat her Latvian opponent and move into the title match at the Aviation club.
Wozniacki lost to Czech Karolina Pliskova in the Doha final last weekend.
"It's been a pretty good couple of weeks for me, I'm very happy with how I have been playing. Very happy how I have managed to get through these two weeks," Wozniacki said.
"It's been very tiring mentally. The fact that I have just been staying in there and keep grinding, I'm kind of proud of that.
"She definitely was a tricky opponent. I knew going into it that she was going to be difficult. She mixes the pace up. She really tries to break your rhythm. I was really pleased with how I was playing. I tried to stay aggressive and tried to mix it up, as well."