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Dominic Thiem and Alexander Zverev both look to reach their first Australian Open final.

Preview: 'No Secrets' When Thiem Meets Zverev

Semi-final clash takes place on Friday

After losing last year’s championship match at the Nitto ATP Finals, Dominic Thiem boldly declared that he’s “pretty sure we’re going to see a new and young Grand Slam champion next year.” That could happen as soon as this week, with the fourth seed battling seventh seed Alexander Zverev on Friday for a place in the Australian Open final.

Having faced Novak Djokovic or Rafael Nadal in three of his four semi-finals at Roland Garros, Thiem is used to being an underdog at this juncture of major championship. He’ll be the on-paper favourite this time when he meets Zverev. Thiem leads their ATP Head2Head rivalry 6-2, including a straight-sets win last year in the semi-finals of the Nitto ATP Finals.

“For me, it's funny because it's the first time in a Grand Slam semi-final that I face a younger guy,” Thiem said. "We’re good friends. I'm happy for him, as well, that he's playing so good here. He made his breakthrough at a Grand Slam.

“We have no secrets from each other. We played so many times, also on very special occasions already, at the [Nitto] ATP Finals, semi-finals, Roland Garros quarter-finals. It's a nice rivalry we have. It's great that we add an Australian Open semi-final to this one.”

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After surviving a five-set scare in the second round against Aussie wild card Alex Bolt, Thiem elevated his game with each match. His marathon four-set victory over top seed Rafael Nadal was a microcosm of all the improvements he’s made over the years.

The Austrian cracked 65 winners, many of them with his beefed-up forehand, and showed his increased willingness to move forward by winning 25 of 33 net points (76%). Thiem’s stamina after four hours of play also reflected his hard work during a grueling pre-season in Miami. Recovering quickly from his intense clash with Nadal will be essential since Thiem has spent far more time on court this tournament (14:33) than Zverev (10:25).

Read & Watch: Thiem's Road To 2020

Zverev can be forgiven for keeping his expectations low after losing all three of his singles matches earlier this month for Team Germany at the ATP Cup, but the 22-year-old is back in business this fortnight. Displaying the tennis that’s brought him 11 ATP Tour titles, including the 2018 season finale at The O2, he’s only dropped one set en route to his best showing at a Grand Slam.

“I was paying too much attention to them. I was just playing better tennis at the other tournaments… The Grand Slams maybe meant too much for me,” Zverev said. "I was doing things, in a way, too professional. I was not talking to anybody. I wasn't going out with friends. I wasn't having dinner. I was almost too focussed."

He changed his tactics this tournament by "doing much more things outside the court" and adopting a more relaxed approach. Instead of pushing too eagerly for his Grand Slam breakthrough, Zverev admitted that he "wasn't really expecting myself in the semi-finals or quarter-finals… Maybe this is a stepping stone. Maybe this is how it should happen. We'll see how it goes in two days."

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Zverev seeks to become just the 10th first-time Grand Slam finalist in the past decade. Only two of those players (Wawrinka & Cilic) went on to take the title.

When the German’s serve is in full flight, he's able to use booming serves to set up one-two punches with his forehand. In his quarter-final clash with No. 15 seed Stan Wawrinka, Zverev landed 84 per cent of his first-serves (63/75) in the last three sets and won 79 per cent (50/63) of his first-serve points.

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Those numbers are a stark contrast from the serve troubles that plagued him over the past 12 months. Zverev averaged 5.9 double faults per match last season and the issue only worsened during the US Open, where he averaged 10.8 per match and hit 17 in his fourth-round defeat to Diego Schwartzman. It appeared that the problem might carry into 2020 after he served 31 double faults in his three matches at the ATP Cup. But Zverev's remarkable turnaround in Melbourne has kept him to just nine double faults in five matches.  

Maintaining that level will be essential against Thiem, who is widely considered one of the best returners in the game. Zverev will need to keep the points short and avoid lengthy rallies with the tireless Austrian. Thiem won 15 of 24 rallies that lasted more than seven shots in his quarter-final with Nadal. The longer the match goes, the more it will likely swing in favor of Thiem, who produced a 15-3 record last year in deciding sets.

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But Zverev will likely have plenty of crowd support as his promise to donate "every single cent" of his prize money to bushfire relief if he takes the title -- more than AU$4 million -- moves closer to fruition. He'll also take confidence in holding wins over the other three players remaining in the draw. If he can defeat them in the world’s biggest ATP Tour events, there’s no reason why he can’t in a Grand Slam.

“I did beat Stan just now, who is also a multiple-Grand Slam champion, which gives me a little bit of confidence that I can do it,” Zverev said. “I hope I can still continue to play better in the semi-finals and hopefully maybe in the final. The people that I'm going to play are not getting worse.”