On the court, CoCo Vandeweghe is all bluster and bravado, an all-or-nothing ball striker with a booming forehand who compares herself to a freight train and shrugs (literally) when she upsets the top player in the world.
Vandeweghe has marched through the Australian Open draw with such confidence, in fact, it's hard to believe she'd ever be intimidated on court.
Yet, after handily beating former French Open champion Garbine Muguruza 6-4, 6-0 to reach her first Grand Slam semifinal on Tuesday, Vandeweghe admitted being quite nervous. If so, she hid it well — and handled the pressure with remarkable poise.
"Maybe I play better nervous and scared," she said. "I think I don't shy away from a challenge necessarily. I never have. Growing up, I've always just been wanting to prove people wrong."
The 25-year-old Vandeweghe, the niece of former NBA player Kiki Vandeweghe and daughter of an Olympic swimmer, has always had the kind of power game to compete with the top players in the game. She won the U.S. Open junior title in 2008 and blasted her way to the quarterfinals of Wimbledon two years ago.
She also has a surprising 6-1 record against top 10 players in the past year — better than Serena Williams' 5-3 mark.
But where Vandeweghe has struggled in the past is with her consistency. She fell in the first round nine times last season and finished the year on a four-match losing streak. The week before the Australian Open, she lost to 103rd-ranked Duan Yingying in Sydney in straight sets.
Her temper has also been an issue. She throws a lot of rackets and berates herself. "I try and behave the best, but it's a work in progress," she said.
Coming into the new year, Vandeweghe decided she needed a new mindset. And it's apparently been paying off.
"When you play tough players like you will in later rounds of tournaments, you can't be showing that you're struggling or not feeling confident in yourself," Vandeweghe said after her 6-2, 6-3 upset of top seed and defending champion Angelique Kerber in the fourth round.
"At least, that's what I decided to tell myself this year ... because I was lacking in confidence in certain tournaments and certain stages. I mean, last year I came here and I didn't even win a match, so here I am now."
The numbers in her last two matches show a more composed player: 30 winners, 20 unforced errors against Kerber, 31 winners, 20 unforced errors against Muguruza. She was broken just once (to Kerber). And against, Muguruza she only lost 10 points in the second set.
"So many weapons, so many places to hurt you with," former top-10 player Mary Joe Fernandez said while commentating her match against Muguzura for ESPN. "She put a pretty good thrashing on Kerber, too. This type of tennis will beat anyone."
Now, Vandeweghe faces Venus Williams for a spot in the final, and as she's made clear in Melbourne, she's not afraid of anybody.
"It's just another person that's in front of me, whoever it may be, if it's No. 1 in the world, No. 130 in the world," she said. "It doesn't matter, it's still an opponent to get in my way of achieving my goals."