France and Spain both needed to come from behind to win their opening Group B matches against China and Australia respectively, and Denmark had to do likewise in Group A after Mardy Fish beat Frederik Nielsen in the men’s singles.
World number eight Fish, who helped the United States win the Hopman Cup in 2008, saw off Nielsen 4-6 7-6 6-4 to give the fourth seeds a winning start at the Burswood Dome.
However, Denmark levelled things up in the women’s singles when world number one Caroline Wozniacki, despite losing five of the opening six games, defeated Bethanie Mattek-Sands 7-6 6-2.
Mattek-Sands won the Hopman Cup last year in partnership with John Isner.
Wozniacki then enjoyed more success over Mattek-Sands as she joined forces with Nielsen to beat the American pair 7-5 6-3 in the mixed doubles
Wozniacki, who came straight to the venue from the airport after travelling from Thailand, said: “It’s been a long day but it’s been a good day. I’m just happy that we played really well and I really enjoyed that mixed doubles.”
“I just flew in today [Monday] a few hours before my match. I came straight here and warmed up, Frederik was playing an unbelievable match against Mardy so I had a little bit of time to settle down.
“I went in and played my singles and played the mixed and now I will probably have some good food and go back to bed.”