Christian Harrison
Harrison and Skupski win Australian Open men's doubles title in first Grand Slam together
Poland dump the US out to set up United Cup final against Switzerland
Gauff helps Team USA past Greece into United Cup semi-finals, Switzerland advance
US reach United Cup quarters despite Gauff shock as Hurkacz upsets Zverev
Jannik Sinner pulls out of US Open mixed doubles tournament with Katerina Siniakova