Many expected this to be the final of the season-ending tournament in Turin, but it is instead a semi-final showdown after Djokovic just about edged through his group.
The world number one was beaten by Jannik Sinner and then had to rely on the Italian to beat Holger Rune to ensure he made it through to the last four and maintained his bid for a record-breaking seventh time.
Alcaraz has not been at his sensational best either, losing his opening match to Alexander Zverev to make it three defeats on the bounce for the Spaniard. Wins over Andrey Rublev and Daniil Medvedev got things back on track though, as he made it through as group winner.
That means the best two players in the world meet for a fourth and final time this year, having already served up three memorable encounters. Djokovic came out on top at Roland Garros as Alcaraz was badly hampered by cramp in the French Open semi-finals, but the Spaniard had no such issues five weeks later as he won an incredible Wimbledon final.
The pair then met at the Cincinnati Open final in August, those three sets taking just under four hours as this time Djokovic emerged victorious from a titanic battle. It would be no surprise if similar drama was served up tonight.
How to watch Alcaraz vs Djokovic
TV channel: The ATP Finals showdown will be broadcast in the UK on the Amazon Prime Video streaming service. The match is scheduled to get underway at 8pm GMT.
Live stream: Amazon Prime subscribers will be able to watch the action either on their website or through the app.