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.

Carlos Alcaraz suffered a loss in his first match at the ATP Finals in Turin. World no. 3 fell to Casper Ruud 6-1, 7-5 in an hour and 25 minutes, wasting a massive advantage in the second set and extending his struggles on an indoor court.

Carlos Alcaraz opened his account at the ATP Finals on Wednesday with an entertaining 6-3, 7-6 (10/8) win over Andrey Rublev, while Casper Ruud missed an early chance to reach the semi-finals after losing in straight sets to Alexander Zverev.