Venus has only beaten Serena once since 2009, but the younger sister has just returned after becoming a mother. "Great way to come back".
Venus achieved victory behind winning 81 per cent of Cirstea's second service points, leading her to six breaks of serve during the match. And I go, 'Serena, you're doing good, you're doing good no matter what.
They will play their 29th competitive match on Monday, with Serena having won 17 of the previous 28.
Not only is Venus now more match fit - this is her 13th WTA event over the past 12 months, and Serena's first - but the earlier in the tournament they play each other, the more it has favoured Venus.
"It's a huge difference to play her in the semifinals or even the quarterfinals or a final as opposed to the third round", she said.
You know, we can always stay in the tournament longer if, you know, the both of us are in the tournament.
That this is Indian Wells, a tournament that holds plenty of history for the Williams sisters, makes it an even more loaded contest.
And when Venus, accompanied by her father Richard, took her seat to watch her sister play Kim Clijsters in the final two days later, the atmosphere turned sour.
The crowd's treatment led to a 14-year boycott by the sisters, which Serena finally ended in 2015. This is just her third appearance in the California desert in 17 years.
"That's totally gone out of my mind", she said. In fact, it's the first time they've met before the Round of 16 since their very first head-to-head matchup more than 20 years ago.
She admitted to feeling rusty in her first two rounds against Zarina Diyas and Kiki Bertens but a wary Venus countered: "She's playing really well and just honing her game".
"I still have a lot to give".
Five-time Grand Slam champion Sharapova is a five-time finalist in Miami but has never won the tournament.
She fell behind 3-1 early in the second set but rallied by holding serve in the fifth game.