For once, tennis eccentric Bethanie Mattek-Sands has stolen the spotlight for her on-court form rather than her wacky outfits or offbeat off-court pursuits.

Mattek-Sands, with the purple hair, tattoos and compression socks, stunned top-seeded titleholder and world No.5 Agnieszka Radwanksa 7-5 6-3 on Tuesday to power into the quarter-finals of the Sydney International.

“Very happy with it. I’ve played her a couple times and I’ve never beaten her, so it’s probably one of the best wins of my career,” she said.

The colourful American is the first player in the professional era to send the women’s champion packing up just one match into Sydney.

Making her victory even more meritorious is the fact it was only her fourth match since breaking down with knee and back injuries last September.

“I’m really happy to be competing right now,” Mattek-Sands said.

“I love playing tennis. I feel that’s just where I’ve been blessed with talent.

“I just always feel that when I’ve gotten hurt, I just haven’t accomplished everything I wanted to accomplish. It’s kind of always having that goal in mind. That’s kind of what brings you back.”

Playing tennis in front of thousands of fans also gives Mattek-Sands the chance to show off her funky dress sense.

“I’m basically kind of wearing whatever I want right now,” she said.

“I’m a pretty colourful person, if that’s hard to believe. It’s just things I’ve found that I like.

“It’s something that I enjoy. I enjoy fashion off the court, so I like it on the court as well.”

Off court, Mattek-Sands confesses to being a pistol-shooting, fast car-loving, off-road-driving adventurer who also enjoys archery and hunting.

“That’s something my husband has done since he’s been a little kid,” she said of her latest hobby.

“We go to the ranges a lot. I actually shoot a bow as well.

“So it’s just something new to try. I like trying new things.”