Serena Williams doesn't try to be intimidating. She just is. The calm and measured way she walks around the court. The slow rock at the baseline as she waits to receive. The quiet fury as she fist-pumps.
But there was a new 'don't mess with me' at Melbourne Park on Wednesday, and no doubt totally unintentionally.
After the blazing heat of Tuesday, Wednesday brought less sun but more humidity, such that walking (let alone running) around felt like being wrapped in a duvet straight from the dryer. And while players, public and press were melting, Serena was out there warming up. In long sleeves. It was a look that means business.
She looks that way on court too. There's something about the long ponytail, headband and black and pink dress that harks back to the year of the black and pink panther suits and the Serena Slam. No ruffles, no flying hooped earrings. It's simple and serious. And so was her tennis.
Serbia's Vesna Dolonc was unlikely to throw an unexpected curve ball at the world No.1. She is the world No.104, with two Grand Slam tournament third rounds to her name and not much else so far. But what we also know about Serena is that she can be her own worst enemy. Not today.
"I was happy just to get that win under my belt and have a chance to go at the next round," she said, beating Dolonc 6-1, 6-2 in an hour and three minutes.
"I have been training for a long, long time in the heat in Florida as well as playing - I have been coming to Melbourne for years and years. So you just have to be ready for those hot conditions and just try to get through it."
Holding serve before the crowd had fully returned from a much-needed rehydration break following Li Na's antics, Serena led 3-0 after a matter of minutes. Dolonc rescued the next game to prevent that, but the set was still Serena's, 6-1 after 29 minutes. Only one rally went beyond nine shots, Serena firing down four aces and seven winners, and forcing errors for both breaks of serve.
There was a bit of gesturing, a little posturing. I'm sure she'd rather not have hit seven unforced errors, and would quite like to get a few more first serves in. But it's the second round.
Two breaks of serve in the second set came courtesy of two double faults from Dolonc, 24 years to Serena's 32, and although she had a glimmer at 1-4, a break point of all things, Serena saved it with an ace.
Dolonc denied Serena the double breadstick, holding serve with a little flash of grit. But the challenge ended there. Boom, boom, boom and boom again, Serena served out to love, burying a serve out wide to the right and a forehand drive volley out wide to the left to win 6-1, 6-2 in an hour and three minutes.
She waved, she twirled, she smiled (briefly).
"It was definitely really hot today," she said afterwards. "I just tried to take it in stride and do the best that I could. Sometimes my body just says no to hot weather. Sometimes I have no reaction.
"I just pretend I'm in Hawaii riding a wave man, it's all I can do," she laughed. "I'm still excited to just be here, to be playing in front of this crowd. I'm just happy to still be alive.
"I have so many matches I have to win in order to do well and in order to lift the trophy. It's such a long way. I'll just have to play one match at a time."
Two matches down, five to go.