Postpublished at 09:17 Greenwich Mean Time 26 January
Jonathan Jurejko
BBC Sport in Melbourne
When the rallies are being extended, it is Zverev who is more likely to break down first.
Sinner has won five of the eight rallies which have gone over nine shots.
Dragging Zverev onto his forehand side has been a particularly effective tactic, with the German feeling more uncomfortable on that wing and being lured into an impatient return.