She couldn't, could she? On tennis's annual manic, marvellous Monday, the never more devoted elder sister couldn't ruin her sibling's grandest march on tennis history? Venus Williams to poop Serena's Grand Slam party? Surely not...
Of all the plot lines on the hectic, exhilarating day when 16 belting matches determine the singles' quarter-finalists, top billing has to be reserved for the latest episode of a 17-year saga between the legendary pair who are so close that having to play each other must feel like, and often looks like, a rare ordeal.
Serena reckoned that if she could watch Monday's match, she would be cheering for Venus. Venus said she would be cheering for Serena.
You see, other families attend Christmas gatherings which feel like an excruciating form of torture; the Williamses just have Centre Court meetings.
This is the sixth, the other five having been in finals and semi-finals, with Serena's advantage less emphatic than you might imagine. She leads 3-2 at Wimbledon, 7-5 in all Grand Slams and 14-11 overall.
Yet they have not faced each other in a Slam for six years and there is a very different dynamic to this fourth-round affair. They share 10 Wimbledon singles titles but Venus, at 35 and battling the immune disorder Sjogren's Syndrome, has tumbled to No.16 in the world while Serena, two years younger, has raced halfway to an historic calendar Grand Slam.
Yet Heather Watson showed up the vulnerability that accompanies the incredible champion spirit within Serena, as the younger sister talked of her negativity and of her feeling that Venus - "the toughest player I've ever played" - was performing better than she.
As ever, even if it's not exhilarating, it will be utterly fascinating.
Serena once described last-16 Monday as the day that Wimbledon becomes "all business". For Andy Murray, raring to go after Saturday's weird tale of two time-outs against Andreas Seppi, that could mean really perilous business on Centre Court, like a trial by 6ft 10in beanpole Ivo Karlovic's serve, still a thing of wonder arrowing in from a rare elevation of beyond 10ft, with kicking bounce at up to 137mph.
The 36-year-old has served 136 aces in three matches and, though Murray's returning prowess has offered up a hard-earned 5-0 career record over Karlovic, the Croat remains on his day what John McEnroe calls "every player's nightmare", rhythm-breaking and morale-sapping.
Champion Novak Djokovic has another explosive serve to defuse on No.1 Court, noting that South African Kevin Anderson is playing "the tennis of his life", but the champion cannot be far from his matchless best himself, having seemingly had more trouble working out where exactly to sign an admirer's prosthetic limb than how to beat three awkward opponents without dropping a set.
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Roger Federer, fresh from taming Sam Groth and his 147mph serve, has his eyes set on an unreal 45th Grand Slam quarter-final appearance, having twice beaten Roberto Bautista Agut, whose breakthrough has been greeted enthusiastically by his great golfing pal, Sergio Garcia.
The women's draw has been flung wide open with Petra Kvitova's dethronement by Jelena Jankovic, the former world No.1 who is now pitted on No.3 Court against 2012 finalist Aga Radwanska, who happily seems to have been rejuvenated by the Eastbourne and Wimbledon greenery.
The 18-year-old Swiss Belinda Bencic could become the youngest ladies' singles quarter-finalist at Wimbledon since Nicole Vaidisova eight years ago, providing she can defeat a reinvigorated Victoria Azarenka on Court 12.
Match of the day? Well, in the last round, Nick Kyrgios stroked the umpire's shoulders, bounced a racket into the crowd, was ordered to turn his headband inside out, received a code violation and took courtside advice from a bloke in a Batman T-shirt, all while playing shots to die for. Against Richard Gasquet on No.2 Court, it is about time the young Australian upped the entertainment value!
