If world number two Azarenka has flown under the radar during this fortnight, it is only because she has made such impressive, untroubled progress.
While a host of her rivals have been flapping and falling, Azarenka has shown little in the way of fragility.
The Belarusian is the only semi-finalist yet to have dropped a set, and until a dramatic finale to her last-eight clash with Tamira Paszek, decided on a second-set tie-break last night, she had not been pushed at all.
There is little question that will change on Thursday, with Williams demonstrating in her quarter-final against last year's winner Petra Kvitova that the bigger the occasion, the greater the threat she poses.
Azarenka knows all about Williams' Wimbledon record: the four titles from six finals in a decade of dominance shared with sister Venus.
She is well aware, too, that Williams has won seven of their eight past meetings.
However the 22-year-old from Minsk is not flinching as the imposing figure of the American looms.
"I don't really like to look back in history," she said, "because every time you step on the court it's a new story.
"You kind of write your own history every time.
"I've lost to her most of the time. But I think we played once here only."
That encounter came three years ago, when Williams won for the loss of five games against a teenage Azarenka in the quarter-finals.
"She's a great champion," Azarenka said.
"It's going to be a tough match no matter what. But that's what you kind of expect to have in the semi-finals. We had good matches. We had bad matches. We'll see."
The obvious objective for Azarenka is to carry off the title. The bonus, should she achieve that, will be her return to world number one status, which she occupied after winning her maiden grand slam at the Australian Open in January.
While Dinara Safina and Caroline Wozniacki have held the number one position in recent years without landing a major, it would take a mean judge to scrutinise Azarenka's performance and conclude she is not worthy of her ranking.
And Williams, who has mithered over the ranking system over the years, has no doubt Azarenka is the real deal.
"She's playing unbelievable. I think she's played so well this year," Williams said.
"Already having a grand slam under her belt is really great. She did it in such style, so it's not going to be easy."
Williams heads into the tussle believing she has "absolutely nothing to lose", positioning herself as the underdog.
That might amount to a stab at mind games, but as sixth seed Williams pointed out: "She's had a better year than I have. She's been so successful already.
"Going against a player like that, I feel like she almost has an advantage."
Williams and Azarenka have survived the bottom half of the draw, with Germany's Angelique Kerber and Poland's Agnieszka Radwanska navigating their route to the last four via the top half.
Radwanska can rise from third to number one in the rankings by carrying off the title.
This is a first grand slam semi-final, though, for the 23-year-old who saw off Russian Maria Kirilenko in the last eight.
As the higher-ranked player - Kerber is the eighth seed - Radwanska is aware she has a great chance to reach the final.
"It's always an opportunity. It doesn't matter who you play," Radwanska said.
"This is the semi-final, so it means that we have both already played a couple of good matches, also against seeded players. It means she's also playing great tennis this tournament.
"Really I have to play at 100% to win that match."
Dipping below her usual standard cost Radwanska at last year's US Open, where Kerber claimed her scalp in the second round.
And Kerber went on to reach the semi-finals, so unlike her opponent she possesses experience at this stage of a grand slam.
"It's one of the best things in my career right now to be in a second semi at the grand slams," Kerber said.
"I will go out there and try my best. I have nothing to lose right now. I will just try to play good tennis and enjoy it. I know I need to play at my highest level to beat her."