Azarenka had never beaten Williams on grass or in a Grand Slam competition coming into the quarter-final meeting, and that drought was prolonged. The official Wimbledon Twitter account noted Williams' impressive Slam winning streak after the match:
Despite the gulf between their Wimbledon seeds, Williams and Azarenka looked bound to endure a close affair from the first game, where the latter fought off a break-point chance before holding serve to go ahead.
Azarenka came into this meeting with a fruitless record against Williams in major tournaments, per ESPN Tennis:
However, a more aggressive approach to Tuesday's encounter paid off, as it was actually the No. 23 seed who broke serve first to go 3-1 ahead in the opening set.
Riath Al-Samarrai of the Daily Mail noted that the pair's infamous grunting was on full display:
Even with a lead, Williams' opponents tend not to feel safe under the American's onslaught of pressure, but Azarenka coped well as she continued her assault on the title contender.
She looked particularly capable when it was her turn to serve, too, as radio and TV presenter Deji Kofi Faremi confirmed a three-game cushion:
Azarenka had the chance to break her foe again, but she settled for a 6-3 victory in the first set with a strong forehand to finish, knowing full well that her job was far from done.
That being said, Ben Rothenberg of the New York Times asserted the world No. 24 stood a far better chance at triumphing with a first set in hand, based on previous clashes with this particular opponent:
Speaking to Tennis.com prior to Tuesday's bout, Azarenka outlined the need to not only match Williams at a major, but to finally show she can indeed prevail over the world No. 1, saying: “Close is not good enough. I need to go out there and prove myself, and that's it. To talk about it is pointless for me. I need to go and do my work on the court.”
There came an early chance to prove that pedigree in the second set, when the score was poised 2-1 in Williams' favour following a back-and-forth of serves in the early exchanges.
Williams pressed Azarenka with a potential break in the fourth game, but the 25-year-old endured an exhausting spell of break points to defend her serve and stay level at 2-2, impressing tennis writer Chris Goldsmith:
That same pressure only grew as Williams started to fare more capably with her return game, pinning Azarenka to the baseline with some of her trademark power.
Azarenka's shot selection was perhaps to be questioned as Williams won the next three games to go 5-2 up:
We've come to know the younger of the Williams siblings for her ability to hit back from slow starts, and Tuesday's showcase was no different as Azarenka began to fade.
As Rothenberg attested, it almost seems inevitable that Williams will revive herself in any given fixture, and Azarenka's faltering first serve in particular started to gift the No. 1 seed too many chances:
If Azarenka's slump wasn't confirmed already, dropping her serve in the second game of the third set certainly did, and the five-time Wimbledon winner established a gulf at 3-0, winning seven games in a row.
Portions of the SW19 crowd spurred Azarenka to end that streak and finally get a game on the board to trail 3-1, but Williams wiped her opponent out in the fifth game with four unreturnable serves to move within two games of victory.
The match ticked closer to what now seemed like an undeniable win for the tournament's top seed, with Williams' victorious cries ringing around Centre Court after what seemed like every point claimed.
As though she was merely biding her time until the match's crescendo, Williams' prolific serving suddenly stepped up a notch, and Courtney Nguyen of Sports Illustrated was left in awe as the ace count rose:
That domination was put into context when she won the seventh game of the third set in just one minute and 15 seconds to soar ahead 5-2:
Azarenka defended her serve to keep the match alive, and it even seemed as though Williams could be in trouble after the underdog took a 30-0 lead in the ninth, decisive game.
There were to be several more cries of "come on" from Williams, though, and Azarenka finally gave way with a wild forehand.
The tournament's official Twitter account passed along a quote from Williams after the match:
Williams must now gather herself before preparing to go up against Sharapova, who defeated CoCo Vandeweghe 6-3, 6-7(3), 6-2 earlier on Tuesday.
Speaking to BBC Sport after Tuesday's triumph, Williams was full of praise for her next opponent and gave off a determined intensity to reach this year's final.
"It's been a while but she's been playing really well, she's such a fighter," Williams said. "I look forward to it. I don't have anything to lose, I'm just going in there trying to win a match."
This will be her first semi-final fixture at Wimbledon since 2012, having exited the tournament in the fourth round and the third round of the 2013 and the 2014 competitions, respectively.
According to the official WTA website, Williams leads Sharapova 17-2 in head-to-head meetings, but both of the Russian's career wins over the American came in 2004.
A slow start on Tuesday left the world No. 1 open to the risk of falling against Azarenka, and Williams will certainly hope to employ more initiative in the final four in her search of a sixth Wimbledon crown.