The USA pairing of Jack Sock and Vicky Duval have ended their Hopman Cup campaign with a win over the Czech Republic – their only victory of the mixed-teams event.

They claimed the tie with a 7-6 (7-5) 4-6 10-7 triumph over Jiri Vesely and Karolina Pliskova in the mixed doubles in Perth on Thursday night.

Earlier, Sock sent down 25 aces to beat Vesely, 4-6 6-2 7-6 (7-3), in the mens singles.

The American world No.26 said that his serve let him down in a disappointing 2015.

So he worked hard on it during the off-season and even sent down a few extra balls in training with good friend Nick Kyrgios, in 42 degree Perth heat, on Thursday, before his match.

His serve gained momentum and the rest of his game followed suit.

“I worked on it a lot in the off season and it feels good right now, so hopefully I can keep it going,” Sock said.

“It’s the only thing that has really felt good all week. From the ground today I felt a lot better, so that is a nice confidence booster going into Auckland next week.”

The win was Sock’s first of the round robin tournament, having lost in straight sets to both Australia Gold’s Lleyton Hewitt and Alex Dolgopolov of the Ukraine.

Pliskova overcame a scare from the lowly ranked Duval to level their tie.

The plucky Duval, ranked 656 in the world, broke her more fancied opponents service game to claim the first set.

However, playing in just her seventh match since August and since being declared cancer free (lymphoma), the 20-year-old American could not keep up the pace with the world No.11 in the second set, which Pliskova won in just 21 minutes before claiming a 4-6 6-1 6-4 victory.

Duval replaced Serena Williams in team USA, the world No.1 nursing a knee injury leading into the Australian Open.

Both teams failed to make Saturday’s Hopman Cup final after the Ukraine secured top spot in Group A early on Thursday with a win over Australia Gold.