ABU DHABI, U.A.E. -- Unseeded players Veronika Kudermetova and Marta Kostyuk each picked up a victory over a higher-ranked foe in the Abu Dhabi WTA Women's Tennis Open quarterfinals on Monday, earning the right to face each other for a spot in the final of the season-opening event.

Kudermetova of Russia shocked No.2 seed Elina Svitolina of Ukraine, 5-7, 6-3, 7-6(3), in a two-and-a-half-hour thriller to claim the fifth Top 10 win of her career. The World No.46 extended her head-to-head rivalry lead over Svitolina, having now upset the World No.5 in both of their two meetings.

Prior to that match on Centre Court, 18-year-old Kostyuk charged back from a first-set blowout to overcome Sara Sorribes Tormo of Spain, 0-6, 6-1, 6-4, and reach the first WTA semifinal of her career. World No.99 Kostyuk reversed the result from their previous meeting, where Sorribes Tormo edged the teenager in the final qualifying round of 2018 Wimbledon.

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"It was actually on my birthday in 2018 Wimbledon," Kostyuk said to the media about her last match with Sorribes Tormo, following her win. "I kind of knew what to expect from her, but still, I didn’t know, because she’s improved a lot since then."

It will be the first meeting between Kudermetova and Kostyuk, with the winner claiming a spot in her maiden WTA singles final.

Svitolina had come through her third-round match against Ekaterina Alexandrova in a final-set tiebreak, but she was unable to repeat the feat two days in a row, as 23-year-old Kudermetova fired 50 winners, including 11 aces, to take the quarterfinal victory. The win puts the Russian into her first semifinal at a tournament of this level.

"It was a really tough match," Kudermetova told the press, after her win. "I think we both played very good. I tried to stay focused until the end. In the first set, I also played not bad, but I didn’t have a lot of chances, Elina played unbelievable. She had good serves today. I tried to fight, I tried to stay focused, and do everything for the win."

Kudermetova had very little trouble on her serve in the early stages of the first set, and the Russian earned the first break point of the day as her fiery forehand grasped her a chance at 3-2. But Svitolina’s serve was also excellent during the opening frame, and the Ukrainian swatted the chance away with her delivery en route to a hold for 3-3.

More breezy service games for both followed through 5-5, but it was in that game where Kudermetova stumbled with a series of miscues, giving Svitolina triple break point. On the third of those opportunities, Svitolina was rewarded with a long backhand error by the Russian, and the No.2 seed had a chance to serve out the set at 6-5.

Kudermetova saved a set point in that game with another fierce forehand, but the Russian shot a return long to cede a second chance to Svitolina. The World No.5 grabbed her moment with a superb service winner to claim a close opener. Svitolina won 60 percent of her second-service points during the set, while Kudermetova claimed only 30 percent of hers during that timeframe.

The Russian, though, rebounded in the second set. After an early exchange of breaks, Kudermetova started to take control midway through the set, slamming an ace to hold for 3-2, then using her backhand to great effect and breaking again for 4-2. Another thundering ace on game point allowed the Russian to consolidate for a commanding 5-2 lead.

Serving for the set at 5-3, Kudermetova knocked off an overhead at 30-30 to reach set point, although she squandered her first chance with a double fault. However, another stirring overhead winner garnered the Russian a second set point, which she converted after setting up a forehand winner with a divine dropshot.

Kudermetova grabbed an immediate lead in the decider, with a quick break for 1-0, and Svitolina had to save break points in order to avoid falling into a greater deficit before holding for 4-2. However, the Ukrainian struck back, blasting a backhand pass down the line to pull level at 4-4.

The Russian again used her power plays to go up a break, taking a 6-5 lead by crushing a forehand return winner on her fourth break point of a typically lengthy game. Svitolina, though, was not done yet, and used a series of heavy forehands to break back straight away and send the third set into a decisive tiebreak.

In the end, it was Kudermetova who grabbed the early 3-0 lead in the breaker and refused to rescind it. A sterling crosscourt backhand to force an error gave the Russian a 6-2 lead and four match points. At 6-3, Kudermetova magically found the sideline with a backhand to wrap up the win.

"I tried to play aggressive, because you know Elina, she has such good defense," Kudermetova stated. "If you want to win, you need to attack, you need to go to the net, finish the point, because she runs unbelievably. You need to do something aggressive to win the points."

In the earlier semifinal, it all went the Spaniard’s way at the start, as Sorribes Tormo stormed to a 6-0 lead after just 24 minutes. The Spaniard never faced a break point in the opening frame, winning all four of her second-service points in the process, and she won 26 of the 35 points played to claim the one-set lead. Sorribes Tormo had just a single unforced error in the first set.

However, after dropping serve and losing a seventh straight game, Kostyuk’s aggressive game began to click into gear. The Ukrainian got on the board with a break for 1-1, and began to take control in the forecourt, putting away a volley for another break for 3-1.

"I started to move my legs better, I started to look at the ball better, and I think the whole picture changed," Kostyuk told the press, regarding the turnaround from 6-0, 1-0. "I stopped missing, and obviously I know that if I’m in the right spot, if I’m at the ball, it’s really tough to get, especially when I’m hitting close to the line."

A brilliant forehand passing winner at the end of a long rally closed out another long game in Kostyuk’s favor, as she charged ahead to 5-1. The Spaniard was unable to stop Kostyuk’s run of games as the teenager coolly served out the set with more tremendous volleying expertise. Kostyuk had 13 winners in the second set, while Sorribes Tormo did not execute any.

After two sets of one-way traffic, the decider was much closer, as the deep, weighty shots of Sorribes Tormo and the net-charging aggression of Kostyuk slammed against each other, resulting in six consecutive breaks. Sorribes Tormo finally quashed that streak, coming out on top in lengthy rallies to hold on for 4-3.

However, Kostyuk kept striking stellar volleys, holding for 4-4 while saving a break point in the process, and then breaking for 5-4, converting her third break point of another long game with a forehand winner at net. The teen smoothly completed the match in the next game, forcing an error with a backhand down the line for victory.

"I honestly still cannot believe I turned this match around," said Kostyuk. "It just kind of feels like a dream."

2021 Abu Dhabi Highlights: Kostyuk ousts Sorribes Tormo