The pair know that barring an upset in the second semi, the winner will take on two-time US Open champion Rafael Nadal in the final.
But nether will ever have such a good chance of reaching the final at Flushing Meadows – not since 2006 has only one of the top four seeds made it to this stage.
Carreno Busta does at least have some experience at the latter stages of the US Open – he reached the doubles final last year with Guillermo Garcia-Lopez only to lose out to Jamie Murray and Bruno Soares.
Kevin Anderson v Pablo Carreno Busta LIVE
9.20pm: We have players! Thank goodness. I thought I might have got the wrong day. Couple of minutes now as Kevin Anderson, with his big black sleeve on the right arm, slams down his last couple of practice serves.
9.10pm: I’m not quite sure what we’re waiting for, but I was promised a nine o’clock start. That said, the Flushing Meadows staff haven’t been particularly fastidious about that sort of thing over the fornight and with no match to follow, they are entitled to take their sweet time. Just build the anticipation, doesn’t it?
8.50pm: Let’s look at the head-to-head record of these two players – which makes pleasant reading for the lower-ranked Kevin Anderson. The South African is 32nd in the world, soon to jump up those rankings on Monday morning, while his Spanish rival Carreno Busta is the last of the top 20.
But Anderson has beaten Carreno Busta both times he has met him, most recently in straight sets in Canada just a few weeks ago.
8.40pm: Right then. The doubles final is over – congratulations to the victors Rojer and Tecau, sad faces for the defeated Lopez and Lopez – and the two debutants in the Grand Slam semi-finals are taking to New York’s biggest tennis stage.
Nearly 30,000 will watch these two play for a place in the final on Arthur Ashe, with millions more watching across the globe from South Africa to Spain.
They will be out to knock up in about 20 minutes’ time.