But for some it brought closure to the once testy relationship between Indian Wells and the sisters who hail from the Los Angeles suburb of Compton. "Serena came roaring back".
"It never crossed my mind", Venus said.
It was their earliest meeting since a 17-year-old Venus beat 16-year-old Serena in the second round of the 1998 Australian Open.
In her first match back, Serena beat Zarina Diyas, the 53rd-ranked player in the world.
No one would dispute that.
Venus took the lead in the first set but a ruthless Serena bounced back to take the next two set, taking the title she had won the previous year. Venus served big when she needed to, although it was a struggle to close out the tie.
Venus closed out the 29th career meeting between the two on her second match point as Serena sailed a forehand long to end the third-round match in front of a crowd of 13,000.
Serena threatened a break, but Venus managed to hold on for the win.
Serena was already pregnant with daughter Alexis Olympia, who was born on 1 September, when she beat Venus 6-4 6-4 in Melbourne at the start of 2017.
"I missed too many shots in the first set".
Venus meanwhile was the more solid, striking 19 winners and 21 unforced errors in the tricky conditions of Indian Wells, where the balls zip through the air but then are tempered by a slow hard court.
Serena said she is still easing her way back into match fitness.
"Obviously I didn't want to play Venus so early on, but it can happen", Serena said following the match.
"So, I just have a long way to go, and I'm looking forward to the journey". "I thought I was in control of the point and winning the point, and she turned it around".
"Of course I played really against Donna in the first round but beating Ashleigh, which I think she's the best player on the WTA player, I think she's by far the best and she can do anything on court, that gave me a lot of confidence actually so I went out there and I was confident in myself. My room for improvement is incredible", added Serena. So I have just got to keep saying each tournament my goal is just to be better than the last. "She was playing the tournament here, and she won juniors".
"[Serena's] level is super high and it was very hard to close out the match, just getting one ball back", Venus said. "[Today was] completely different, a completely different resolution to solving the problems and the rallies on the court".
"I didn't really care about what she was doing on the other side of the net".
If Williams makes it through her quarterfinal match, she will again play back-to-back matches Thursday and Friday.