Following Aryna Sabalenka's incredible run to the Australian Open title, I spoke to Gavin MacMillan, the biomechanics trainer responsible for fixing Aryna Sabalenka's serve.

0:22: Gavin MacMillan’s own experience with serve coaching.
5:17: The technical changes Gavin made to Aryna Sabalenka’s serve.
11:35: Changing the Sabalenka groundstrokes.
14:43: How the changes translated to her win against Elena Rybakina.
24:44: Where’s the limit for Sabalenka?