Venus v Serena: it sounds like some intergalactic showdown to save the planet rather than a tennis match between the two members of the Williams family who over nearly two decades have simultaneously dominated their sport like no one else.

And yet, for all their genetic gifts, for all their titles and talent and riches, their quarter-final in the 2015 US Open – which may even be the last of their 27 contests – has landed on schedule like some alien ship, an event no one predicted at the start of the tournament and one laden with enough sub-plots to qualify as an episode of Days Of Our Lives.

That American soap opera celebrates its 50th birthday in November but in that time even its demented scriptwriters might not have come up with a storyline as fanciful as the climax to the real-life saga of The Williams Sisters, So Out Of Compton that will play out in the packed-to-the-rafters Arthur Ashe Stadium.

Exclusion

Over the years both have suffered the exclusion from the main stage of tournaments in the early rounds – from Melbourne to Wimbledon, from Paris to New York – when their records have suggested either or both of them were the main attraction. Subliminal prejudice? It is hard to say but often the TV programme-planners have come up with other matches to show in prime time while the Williams sisters have been sent to a lesser court.

This time there is no doubt about the time and the venue but enough uncertainty about the result to lend intrigue to a match that normally would be a gift for Serena, who has established such hegemony in the women’s game that John McEnroe felt moved recently to boast he could beat her, even at 56. There are more than a few people in tennis who would like to see him try – but Serena is not one of them.

She is like the heavyweight champion of the world: she doesn’t need washed-up pugs. She has been beating real contenders all her career and, as she moves to within three wins of securing the first calendar grand slam since Steffi Graf’s in 1988, her energies are trained now on the person she cares for most in the world but whom she must destroy in public for the 16th time.

There is no avoiding the issue here: there will be plenty of people watching who will wonder how hard Venus (seven slam titles), the elder sister whose career has been in the margins for several years, will try to block Serena (21 majors) on her gilded path to the biggest prize of her career.

Venus said after winning her fourth match here – 6-2, 6-1 over the Estonian qualifier with the English accent, Anett Kontaveit, on Sunday – that this would be “fun”, the fallback description for everything in tennis. Serena, after her most angst-free performance of the tournament, a 6-3, 6-3 win over Madison Keys, expanded on the theme.

Opportunity

“I would agree, I think it’s more fun than it used to be. We really relish the opportunity. We’re both happy to still be involved in getting so far. And it’s still super intense. She’s doing well and she wants to win this. So do I. It’s not easy.”

The gut instinct that has made them both such wonderful competitors most likely will prevail and Venus, who has been playing the more consistent tennis here, will look across the net and see not her sister but someone standing on her highway back to the higher reaches of the game, someone she has played in eight slam finals, someone with whom she has won 13 slam doubles titles and three Olympic gold medals.

Neither of them will falter in the shot. It is in their DNA. They are predators and killers on the court. Otherwise they do not survive, especially in a sport where a single point among possibly more than a hundred can turn the match on its head. Guardian Service