Spain's Carlos Alcaraz suffered a shock 6-1 7-5 defeat against Norway's Casper Ruud in his opening match at the ATP Finals as his hopes of winning the year-end title for the first time suffered a big blow on Monday.

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 on Monday. It marked Ruud’s first victory over Alcaraz in five career meetings,

Carlos Alcaraz looked little like the player who won two Grand Slams this year in a 6-1, 7-5 loss to Casper Ruud at the ATP Finals

Norway's Casper Ruud eased to a straight-sets victory over Carlos Alcaraz on Monday as the Spanish star's bid for a maiden ATP Finals title got off to a poor start.

Casper Ruud’s first victory over Alcaraz in 5 career meetings could make it difficult for the Spaniard with Germany’s Zverev on a hot streak.

Germany's Alexander Zverev, the only two-time champion in the Nitto ATP Finals field, opened his play in the event with a 6-4, 6-4 victory over Russia's Andrey Rublev on Monday in Turin, Italy.