Carlos Alcaraz made a stuttering start to the ATP Finals in Turin as he suffered a shock first career defeat to the world No 7 Casper Ruud.

The two-time Wimbledon champion, who won the first of his four grand slam titles by beating Ruud in the 2022 US Open final, went into the contest leading the head-to-head results 4-0.

But the inspired ­Norwegian Ruud impressively claimed a milestone ­success in the opening match of the John Newcombe Group, winning 6-1, 7-5 in an hour and 25 minutes.

“It’s only one match but it’s definitely one of the best wins of the season for me in terms of who I’m playing, his level, his ranking,” Ruud said in an on-court interview. “I feel very happy, of course. I think we will see Carlos play better tennis than he did today but I took care of my chances and it was a great win for me. Hopefully I can build on it.”

Alcaraz twice failed to hold serve in the opening six games, while he was unable to capitalise on five break points as he surrendered the first set in 36 minutes.

The 21-year-old Spaniard initially appeared to have restored order during a strong start to set two. But he then blew a 5-2 lead, losing five games in a row for the second successive set before swiftly departing court after his surprise loss.

“I knew he was maybe dealing with a bit of a cold,” the 25-year-old Ruud said of the world No 3. “I’ve seen him snuffling around in the area here and always with a tissue for his nose.

“Of course, that’s sad, that’s not good for him, but it’s also part of the game and I knew it coming in. I tried to make him play rallies and do my best but it’s not easy because, when you know someone is not 100%, maybe you get stressed yourself, thinking this is a really big chance for me to maybe win.

“I just tried to stay in my world, in the moment. Luckily, I got a good start and the second set I was able to turn it around with some good tennis at the end.”