PERTH, Australia (AP) — CoCo Vandeweghe gave the United States an early lead and Jack Sock clinched the Americans' opening match Sunday at the Hopman Cup mixed teams tournament.
Vandeweghe beat Lucie Hradecka 6-4, 6-2 before Sock defeated Adam Pavlasek 7-5, 3-6, 6-3 to clinch the match against Czech Republic.
The two Americans also beat Pavlasek and Hradecka 2-4, 4-2, 4-1 in the mixed doubles, which this year features the Fast4 format, including a tiebreaker at 3-3 in each set and no advantage on points.
Hradecka replaced two-time Wimbledon champion Petra Kvitova after Kvitova was injured 10 days ago in a knife attack by an intruder in her home in the town of Prostejov. Kvitova is expected to be off the tour for up to six months.
"I played a decently clean match, it's always going to be a little bit interesting your first time out on the court," Vandeweghe said. "A little pre-match jitters but I thought I did a good job."
The United States has won the Hopman Cup a record six times in the tournament's 28-year history.
Defending champions Australia, represented by Russian-born Daria Gavrilova and Nick Kyrgios, lost the late match Sunday against Spain. Kyrgios beat Feliciano Lopez 6-3, 6-4 in the opener before Spain's Lara Arruabarrena defeated Gavrilova 7-5, 6-1. Spain won the mixed doubles 4-0, 4-2 involving the same players.
Roger Federer, making his return after a six-month left knee injury layoff, and Belinda Bencic begin play for Switzerland against Britain, represented by Heather Wilson and Dan Evans, on Monday night.