Carlos Alcaraz will spend a nervous week watching the ATP Finals as Rafael Nadal and Stefanos Tsitsipas bid to usurp the Spanish teenager as year-end men's world number one.
The top-ranked Alcaraz is powerless to stop his rivals because he is out with an abdomen injury he suffered at the Paris Masters over a week ago.
Nadal will hope he has shaken off the rustiness he displayed in Paris when he lost in his first singles match in two months after spending time at home in Mallorca with his wife and newborn son. The 36-year-old fell to American journeyman Tommy Paul.
The surest way for Nadal, who won the Australian and French Open titles in 2022 and is ranked second, to finish year-end number one for a sixth time is by winning the title in Turin.
Yet he is seemingly unconcerned about joining Pete Sampras in second on the all-time list of year end number ones.
"Like I've often said, it's not a priority for me anymore, because you need a consistency of results that is really only possible for the younger players," he told the Gazzettadello Sport.
"And to be honest I don't like talking about what could happen in the future."
Nadal could also top the rankings if he wins all three of his Green Group games and reaches the final while Tsiptsipas stumbles.
The third-ranked Greek, who is in the Red Group, needs to win all his matches on his way to the title.
Nadal would topple US Open champion Alcaraz if the two Spaniards finish level on points. Nadal has a better overall record in the Grand Slams and Masters tournaments
Nadal opens his campaign on Sunday against big-serving American Taylor Fritz. His other two group rivals are Norwegian Casper Ruud and in-form Canadian Felix Auger-Aliassime.
Tsitsipas, who has never been higher than third, has a very different attitude to Nadal.
"The rankings are there for a reason. They signify something important," he said in August when he regained third spot.
"I think that the very next step would be the No. 1 spot, which I hope I can get to one day."