The United Cup has returned for the third consecutive year as part of the Australian summer of tennis calendar.Some of the world's best players are being pitted against each other in the ATP-WTA mixed-team event.

Alexander Zverev of Germany hits a return during the men singles match against Thiago Monteiro of Brazil in the Group

Borna Coric of Croatia serves during the men singles match against Felix Auger-Aliassime of Canada in the Group A rou

China and Brazil will kick off Group E of the United Cup on Friday in Perth, Australia. With defending champions Germany in the same group, this becomes a crucial tie for both teams.