PERTH: They'll be the tournament's odd couple on the court but emerging US youngster Melanie Oudin believes she and teammate John Isner can be a threat in the mixed teams Hopman Cup, starting on Saturday.

The Americans are seeded seventh in the unique eight-nation event, but Oudin showed at last year's US Open and Wimbledon that she was more than capable of springing a surprise.

Oudin reached the fourth round at Wimbledon, defeating Jelena Jankovic in the process, and then went one better at the US Open, reaching the quarter finals, with Hopman Cup rival Elena Dementieva and former world No.1 Maria Sharapova among her scalps.

Speaking here on Friday, the 18-year-old Oudin said she didn't fear any of her Hopman cup rivals.

"I pulled it off at the US Open and maybe we can pull it off here," she said.

"Everyone in the draw is tough but I think doing well at Wimbledon and the US Open this past year really helps my confidence.

"Going into (tournaments) now I won?t be afraid who I play in the first round or within the draw."

Oudin, ranked 48th in the world, and Isner open their Hopman Cup campaign against Spaniards Tommy Robredo and Maria Jose Martinez Sanchez on Sunday.

Playing the seasoned Martinez Sanchez will be a new experience for Oudin.

"I?ve never played her before but I know she?s a lefty and I know she?s got a strong serve and is really good at doubles and she is going to be coming into the net against me a lot," she said.

"It should be a good match."

The Americans then face top seeds and home side Australia on Tuesday, which will pit Oudin against world No.13 Samantha Stosur.

Oudin and Isner will make an interesting pairing in the often deciding mixed doubles rubbers here, with Isner standing 206cm (6.9 feet) and Oudin just 168cm (5.6 feet).

"Fifteen inches is quite a big difference and I think it?s going to be pretty funny when we play mixed doubles," Oudin said.

"I?ve played (mixed doubles) only a few times but I?ve had a really good time when I?ve played so I?m looking forward to it and it should be fun."

Oudin said she had taken great confidence out of her results in 2009 and was looking forward to continuing to rise up the rankings this year.