Carlos Alcaraz loses to Alexander Zverev in his debut at ATP Finals

TURIN, Italy — Considering all that he's accomplished over the last two years — winning two Grand Slam titles and finishing last season as No. 1 — Carlos Alcaraz no doubt belongs among the world's elite.

Still, this couldn't have been the debut that the 20-year-old Spaniard was hoping for at the season-ending event for the year's top eight players.

After missing the ATP Finals last year because of an abdominal injury, Alcaraz was beaten in his opening match of this season's competition by two-time champion Alexander Zverev 6-7 (3), 6-3, 6-4 on Monday.

Zverev also missed last year's edition after tearing ligaments in his right ankle during a French Open semifinal loss to Rafael Nadal. But the big-serving German clearly likes the fast conditions inside the Pala Alpitour — where he claimed the title two years ago.

Zverev served 16 aces to Alcaraz's 11, saved five of six break points, and never really let Alcaraz feel in control.

Zverev overcame a scare late in the third set when he was chasing down a forehand from Alcaraz, lost his grip, slipped and fell to the court clutching his left ankle. But Zverev quickly shook it off and held in that game for a 4-2 lead.

"I didn't twist my ankle. I just kind of slipped,'' Zverev said.

Zverev faced a break point while serving for the match and responded with an ace down the T. Two points later, the match was over.

Zverev has also had off-court issues recently after a German court issued a penalty order against him after allegations that he caused bodily harm to a woman. Zverev has disputed the allegations and is contesting the penalty order.

Alcaraz can still hope to advance from the round-robin format, with the top two finishers in each four-man group reaching the semifinals.

Later in the red group, Daniil Medvedev and Andrey Rublev were to meet in their opening match.

Novak Djokovic and Jannik Sinner won their opening matches in the green group on Sunday.