Australia's Samantha Stosur admitted she "went off the boil" as pre-tournament favourite Germany rallied for a 2-1 victory in their opening Hopman Cup tie in Perth.

Australia's team of Wayne Arthurs and Stosur, both renowned doubles players, was heavily favoured to claim the tie when it went into the mixed doubles locked at 1-1 at the Burswood Dome.

Germany's Nicolas Kiefer admitted prior to the deciding match he had never played a mixed doubles match in his 11-year career.

But it mattered little as he and Anna-Lena Groenefeld earned a nail-biting 4-6 6-3 10-8 victory, sealing the contest in the deciding match tie-break.

Australia broke Kiefer's serve in the opening match and appeared to be cruising when it won the first set in just 33 minutes.

But the Germans switched tactics from the start of the second set, with Groenefeld serving first.

It paid immediate dividends as they claimed a tight second set, before winning the match tie-break on their third match point.

"It was a tough day," said Stosur, who was broken twice in the second set.

"It's always hard to lose, especially in a tie-break.

"Those tie-breaks can go either way.

"I went off the boil a bit at the start of the second set and found it hard to get back into it.

"They picked up their game and ended up playing better when they switched."

Many pundits were surprised when SportsTAB installed Germany a $3.25 favourite entering the 18th Hopman Cup, with Australia back in sixth at $8.00.

Stosur gave Australia the ideal start in her Hopman Cup debut, beating Groenefeld 6-3 7-5 in the opening singles match for a 1-0 lead.

Arthurs then struggled in his singles rubber, losing 6-3 6-4 to Kiefer, a former world No.4 and six-time ATP tournament winner.

Injury was added to insult when Arthurs came out for the mixed doubles sporting a bandage around his right calf.

But the partisan crowd was still expecting an Australian doubles victory.

Stosur ended 2005 as the world's No.2 ranked doubles player, winning the US Open alongside American Lisa Raymond and the mixed doubles at the Australian Open with Scott Draper.

Arthurs also has an outstanding doubles resume with 12 career titles, qualifying for this year's Tennis Masters Cup alongside compatriot Paul Hanley.

Contrast that with mixed doubles rookie Kiefer.

But he came through with flying colours as he attempts to resurrect his career, much to Groenefeld's delight.

"Pretty impressive, yeah?" Groenefeld said of her partner.

"It was his first one and we have two more for sure and hope we can keep it up."

A disappointed Stosur was looking forward to Tuesday's match-up with the Netherlands.

"I'm really happy with how I played in my singles," she said.

"Hopefully I can keep it going in the mixed doubles next time."

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