MELBOURNE -- Chinese tennis star Zheng Qinwen crashed out of the Australian Open after being knocked out in straight sets by an aggressive Laura Siegemund of Germany in the second round on Wednesday.

Fifth seed Zheng's trusted serve let her down and she had no answers for the German veteran, who prevailed 7-6 (3), 6-3 in two hours and 16 minutes at John Cain Arena.

It was a bitter disappointment for Zheng, whose hope of a maiden Grand Slam triumph was undone by a first-serve percentage of just 56 percent.

Zheng, last year's finalist, had overcome a rusty performance against Romanian qualifier Anca Todoni in her opener.

She was a strong favorite against 97th-ranked Siegemund, a wily veteran striving to make the third round in Melbourne for a second time in three years.

Zheng hoped to come out of the blocks quickly after a sluggish start against Todoni. She showed off her athleticism in the third game with swift court coverage, leading to a forehand winner.

But Siegemund proved formidable opposition forcing Zheng to fire aces and unleash winners after a marathon third game.

Zheng failed to convert a breakpoint in the fourth and eighth games while she continued to struggle to hold serve in the face of brilliant returns from Siegemund.

Zheng's serve finally cracked in the ninth game and she appeared poised to fall one set down until her fighting qualities helped her break and level at 5-5.

But Zheng was powerless in the tiebreak and forced into errors by a relentless Siegemund hitting the lines with precision.

A rattled Zheng was staring down the barrel after losing her serve to fall behind 0-2 in the second set. But she broke in a nerve-jangling third game until falling apart in the fourth game on serve amid time violation warnings.

Zheng tried to rally but Siegemund was not to be denied as she slumped to the ground in celebration.

"I try what I can do during this match. I feel maybe today is not my day," Zheng told reporters after the match. "There are a lot of details in the important points. I didn't make the right choice."

Answering questions about the time serve code violation in the second set, Zheng said it "obviously" distracted her from the match and agreed that the time clock needs to be a bit more visible.

"Yeah, it's better straightaway to the wall instead of on the side," she said. "But, I mean, I get disturbed from that one, but I don't lose the match for that."

Zheng said there was some injury to her elbow.

"I still have an injury and I played with a slight pain. It affected me occasionally and I am not fully recovered," she said. "I think in fact, not playing warm-up matches has no effect on me, today I mainly did not play well on the court."

Siegemund will play either 27th seed Anastasia Pavlyuchenkova or Anastasia Potapova in the third round.

"I knew I had to play more than my best tennis," said Siegemund, who beat a top-10 opponent for the first time since 2022.

"I had nothing to lose. She is an amazing player and one of the best players right now, but I know I can play well," she added.