Next Monday Andy Murray's ranking will slip to 18. Is it all downhill from here? Is this it for Britain's greatest ball sports competitor of the last decade?
Even he doesn't know the answer, and the doubts will be killing him inside, as the pain from his damaged hip grinds him to a standstill on the outside.
His poignant statement announcing his withdrawal from the Brisbane International tournament this week laid bare how much his sport means to him.
"The little kid inside me just wants to play tennis and compete. I genuinely miss it so much and I would give anything to be back out there," he wrote.
From there it was a matter of time before the inevitable confirmation that he would miss the year's first grand slam, the Australian Open, the tournament in which he's been runner-up an agonising five times, and the event on which all his rehabilitation work has been focused these past six months.
The championship will also be missing former world number four Kei Nishikori when it starts on 15 January. Doubts still hang over the participation of Rafael Nadal and Novak Djokovic, as the intensely physical demands of modern tennis take their toll.
Even the phenomenal Roger Federer has prospered only through a drastic pruning of his schedule.
Murray last competed at Wimbledon in July. Walking close behind him there, it was almost painful to watch him limp along.
He opted then for rest and rehab, rather than surgery.
Now, he says: "I'll be flying home shortly to assess all the options".
That includes the knife, but the Scot adds: "The chances of a successful outcome are not as I high as I would like, which has made this my secondary option and my hope has been to avoid that."
Another former Wimbledon champion, Lleyton Hewitt, offers some optimism. He had surgery on both hips and returned to win tournaments, but not at grand slam level.
Murray has talked about settling, if necessary, for being able to compete at the standard of a top-30 player.
Some change, that, for the ultra-competitive reigning Olympic champion and three-times grand slam winner.
If he means it, we may yet see him grace the tennis courts of the world beyond his 31st birthday in May.
But Wimbledon finals, Olympic glory, that status as best in the world? It feels an improbably long way back.