By December 2010, Novak Djokovic was just about to finish his fourth straight year ranked number three in the world. There he stood, behind the dominant players of the ‘00s, Roger Federer and Rafael Nadal. As of that point, Federer had won 16 majors, Nadal nine. Each had also captured a precious career sweep of all four Grand Slams.

Djokovic by then had won one, the ’08 Australian Open, an effort highlighted by a win over Federer in the semis. He’d also reached two other major finals, both at the US Open, the first in ’07, the second coming three years later. One notable aspect of Djokovic’s ’10 New York run was that in the semis, he’d rallied from two match points down to beat Federer.

Two thousand ten was also the year Djokovic made a major dietary change. He eliminated gluten from his diet and rapidly felt more energetic, far less prone to the fatigue that had surfaced in several prior matches.

But there was another major factor that fueled Djokovic throughout the first year of the new decade. This was a man who took tremendous pride in his national identity. Djokovic had first played Davis Cup for a combined Serbia-Montenegro team as a 16-year-old, winning a dead rubber versus Latvia in 2004 during a Group II tie. By 2010, Serbia was a full-fledged member of the event’s highest level of competition, the World Group. All throughout 2010, Djokovic led the team, winning two matches in every tie.

By December, Serbia had reached the finals for the first time, up against France.

Inside Belgrade Arena, the crowd was lively and eager for its players to claim the prestigious title. But it took a lot of effort—three days of rollercoaster-like scores. Day one began with Frenchman Gael Monfils beating Janko Tipsarevic by the rarely seen score of 6-1, 7-6 (4), 6-0. Djokovic put Serbia on even footing with a commanding 6-3, 6-1, 7-5 victory over Gilles Simon.

Davis Cup ties have often pivoted around the doubles. This match was a thriller. Serbian doubles veteran Nenad Zimonjic paired up with Viktor Troicki to take a two sets to love lead over the French team of Michael Llodra and Arnaud Clement. Though the Serbs won the first two sets, the French duo rallied, eventually taking the four-hour and 34-minute epic, 3-6, 6-7 (3), 6-3, 7-5, 6-4.

To win the tie, Serbia would have to win both matches on the final day—December 5, 2010.

Djokovic began with a convincing win over Monfils, 6-2, 6-2, 6-4.

So it fell to Troicki and Llodra. With his team and the entire arena cheering him on, Troicki played excellent tennis to win the match, 6-2, 6-2, 6-3. “This is unbelievable,” said Troicki. “I don’t know how to react, what to do. This is the best moment of my life.”

Though Troicki had been the hero in the final match, all knew that the heart and soul of Serbia’s success was Djokovic. “It was unbelievable today,” said Djokovic. “Under the circumstances, maybe one of the best matches I have played this year. It was definitely a lot of pressure, expectations.”

The Davis Cup win proved a major catalyst. Djokovic kicked off 2011 with a title run at the Australian Open. He’d dominate the sport all year long, also winning at Wimbledon and the US Open. And by the end of Wimbledon 2020, he’d stand alongside Federer and Nadal on the Grand Slam tally front—20 majors apiece.