The ATP has listed various scenarios that could help Alcaraz qualify for the final four. The most intriguing one is that if Alcaraz defeats Zverev in straight sets and Ruud beats Rublev in three sets, the Spaniard would win the group and Zverev would finish second.

On Monday, Casper Ruud rolled over Carlos Alcaraz in the first round of the ATP Finals. After losing in straight sets to Ruud, Alcaraz gave three excuses for his poor play. One of the most important reasons was his health.

TURIN, Italy — Carlos Alcaraz struggled with a stomach issue and looked far from the player who won two Grand Slams this year in losing to Casper Ruud 6-1, 7-5 at the ATP Finals.