Despite facing a scare against Aussie Alex Bolt in Round 2, Thiem has had a largely excellent Aus Open campaign. He claimed two top 10 scalps, beating Monfils in straight sets and Nadal in 4.
Zverev has had a similarly impressive run, although he hasn’t faced the same level of quality that Thiem has. He was a comfortable favourite in every match thus far, only beating Rublev and Wawrinka as seeded players.
Thiem is known as one of the best return men on tour, which is a major reason behind his immense success on clay. He is averaging 5 breaks per match so far and I can see him succeeding on the Zverev serve.
Thiem also has the experience edge here, especially at this stage of a grand slam. Zverev has never made it to a grand slam semi before, whereas Thiem has done it 4 times, even making it to 2 finals.
This has the makings of a competitive 4 or 5-setter with very little between these two players. Ultimately, I think Thiem’s experience and edge in the return game give him the win here.