Second-ranked Alex Zverev lost 2-6, 6-3, 7-5 to fellow big-hitter Matteo Berrettini in the second round of the Monte Carlo Masters on Tuesday in Monaco.

The unseeded Berrettini secured victory when serving for the match for the second time and on his first match point against the top-seeded German.

"I wasn't hitting my forehand and serve like I had in previous days," said Berrettini, who has won 17 of his past 18 matches on clay. "I told myself to be more aggressive."

Zverev, the French Open runner-up last year, got the crowd going at the first big clay-court tournament of the year when he won a point with a sliced backhand volley at the net in the fifth game.

But the 28-year-old Berrettini, a Wimbledon runner-up in 2021, broke in the seventh game of the deciding set and then served for the match at 5-4, only for Zverev to break back.

After an intense 11th game, featuring a 48-stroke rally at deuce won by Berrettini, the Italian earned another break of serve and another chance to serve out the match. Victory came when Zverev's two-handed backhand hit the net.

Berrettini, who next faces either Jiri Lehecka or 13th-seeded Lorenzo Musetti, soaked up the applause from the crowd.

The last Italian to win the tournament was Fabio Fognini in 2019, and that year he enjoyed strong vocal support from many Italians crossing over the nearby border.

In second-round matches later Tuesday, three-time champion Stefanos Tsitsipas of Greece began his title defence against Australian Jordan Thompson, and U.S. Open semifinalist Jack Draper faced Marcos Giron.

Ailing Rune retires from opening match

In remaining first-round matches Tuesday, Holger Rune of Denmark was trailing 6-2, 3-0 against Nuno Borges when he retired after feeling unwell.

Rune took a medical timeout at the end of the first set.

"I clearly saw that he wasn't feeling great," Borges said.

No. 15-seeded Bulgarian Grigor Dimitrov beat Nicolas Jarry 6-3, 6-4 on his seventh match point and next meets wild card entry Valentin Vacherot of Monaco.

There were also first-round wins for Alexei Popyrin, veteran Roberto Bautista Agut and Tomas Machac.

On Wednesday, two-time champion Novak Djokovic faces Alejandro Tabilo, who handed the 24-time Grand Slam champion a surprising loss at the Italian Open last year.

Djokovic is seeking the 100th title of his career and recently lost the Miami Open final to Jakub Mensik.