DUBAI, UAE - Qualifier Zhu Lin scored the biggest win of her career in the first round of the Dubai Duty Free Tennis Championships on Monday.

The 25-year-old from China outlasted Qatar Total Open champion and No.16 seed Elise Mertens in a nearly three-hour epic, 5-7, 6-4, 7-5 to move through to the second round of the Premier 5 event. 

"She's a competitor. She always fight until the end of match. I really happy that I'm the winner today," Zhu said after the match.

"I know how she plays because we played last year once, and I lost. I know it's always going to be tough to play against her. I prepared before this match, and I talked to my coach. We [did] very well."

From 4-1 and 5-3 down in the opening set, the World No.16 rallied for a one-set lead, and ultimately looked poised for another comeback and she dug deep to get back on serve after trailing 5-1 in the second set.

"I think when I was 5-3 in the first set, I was kind of like, 'Oh, I'm 5-3.' I kind of forgot what I have to focus on," Zhu revealed. 

"Then after I lost my first set, I think, 'I have to focus on what my coach tell me, play my tennis.'"

Nonetheless, Zhu sent the match to a decider by winning an epic 10th game which saw five deuces and four total set points, and she later rallied from a 3-1 final set deficit of her own to seal a spot in the second round opposite World No.24 Lesia Tsurenko.

"I think we both tired because I been play like six matches, including last week," Zhu added.

"I was really nervous, honestly. It's a very important match for me. I just kept focus on the ball, watch the ball - that's it."

The win for the World No.107 is the second Top 20 victory of her career, but best in terms of ranking. She previously defeated then-World No.17 Petra Kvitova at the Tiajin Open in 2017.

"I think I finally break the top 100. It means a lot for me," she said. "I been working on this goal for, like, a few years now. I've finally done it. I'm so happy right now. There's no words can describe how happy I am."