MELBOURNE, Australia - Down but never out, Germany's Laura Siegemund sprung a dramatic upset on the second day of the Australian Open on Tuesday, rallying from a set and a break deficit to defeat two-time champion Victoria Azarenka, 6-7(5), 6-4, 6-2.

The German trailed 7-6(5), 4-2 in the opening round encounter in Melbourne Arena, but by the end of an almost three-hour marathon, the World No.110 came away with a dramatic victory. 

"I played a good first set and even though I was up in the tiebreak, I let go a little bit and she was right there," Siegemund said after the match.

"I kind of reset myself and knew I was playing a good match, and I just had to to close in those situations. In the third set, I stayed very focused. I knew she wasn't going to hand me the match, and I just had to [take] it."

Using her variety to great effect, the former World No.27 broke serve seven times and out-winnered Azarenka by a margin of 37-29, as both hit 40 unforced errors for the match. 

After breaking twice en route to winning the last four games of the second set, Siegemund won three more return games in the final set, but it was a clutch service game late in the decider that helped decide the match.

After the pair traded breaks to begin the set, with Azarenka moving ahead first, the 30-year-old saved a break point in the fifth game before claiming the Belarusian's serve once more to move ahead 4-2.

The former World No.1 had a chance to hit back immediately, as she built a 0-40 lead in the ensuing game, but struggled to find the court off the forehand side.

Azarenka ultimately had the door to a comeback shut frome there, as Siegemund won five straight points to win the game, and nine of the last 10 overall to win the match. 

The win is the German's first at a major since the 2016 US Open, as her comeback from a major knee injury she suffered in May of 2017 began last April, and she entered the Australian Open with a protected ranking.

"I had a tough journey to come back, and my ranking right now is on the way back up, but to play in this arena, that's what I want to do. It's a hard way back after the injury that I had, and I'm just enjoying it so much."

- Laura Siegemund

Azarenka built her initial lead in the match with a comeback of her own, as she rallied from a break down twice in the opening set before winning the final five points of the tiebreak.

Trailing 5-2 in the breaker, Azarenka hammered down a pair of big serves to stay in touch, and ultimately, a crucial doublt fault off the German's racquet at 5-5 proved key to the Belarusian claiming the first set. 

Should the German want to return to the third round in Melbourne for the second time in her career, she'll need to spring another upset.

Siegemund will face No.28 seed Hsieh Su-wei, whose run to the fourth round a year ago began her singles resurgence, after the latter needed just 58 minutes to see off Stefanie Voegele in her first round match, 6-2, 6-1.