The victory meant that the 22-year-old Spaniard also secured group victory in the Jimmy Connors group in the playoffs.
This means his rival Jannik Sinner has no chance of being ranked first, even if he were to defend last year's title in the ATP playoffs. Sinner has won the second group in the playoffs, the Björn Borg group.
Alcaraz won his 70th match of the season and the Spaniard has also won two grand slam victories during the year.
Alcaraz will face the winner between Alexander Zverev and Felix Auger-Aliassime in the semifinals on Saturday while Jannik Sinner faces Alex de Minaur, Australia.
