Roger Federer. Rafael Nadal. Novak Djokovic. Andy Murray. These four tennis superstars, collectively known as the Big Four, have ruled tennis for the past decade, with each of them taking a turn at the top. In total, they have won 48 out of the last 56 Grand Slam dating back to Federer’s first Wimbledon in 2003. . For the past 14 years, they have dominated almost every tournament and produced one of the biggest rivalries of all time: Federer vs. Nadal.

This past year has been a throwback to the years of Federer-Nadal dominance. Though both players appeared to be declining veterans, Federer won this year’s Australian Open and Nadal won the French Open last month. Though the Big Four are now all over the age of 30, they do not seem to be slowing down in any way.. However, there will come a time in the (hopefully distant) future when they will all retire, relinquishing their hold on the tennis world. Injuries and lack of motivation might start to creep in as the years roll by, and eventually a new generation of tennis players will take over.

Some of these players have been labeled as the NextGen by many tennis experts and commentators because the Big Four’s dominance has stretched for so long.. These players are only 21 and younger, but have been marked as stars to watch in the future. Although the NextGen stars are considered exciting, there are some players in their mid-20s who could also possibly usurp the Big Four. With many new players starting to break onto the professional tennis scene, here are some of the players who will most likely bring the dawn of a new tennis era.

Alexander Zverev Jr.

Age: 20
Country: Germany
NextGen: Yes
Ranking: 12

Alexander “Sascha” Zverev is a tennis player from Germany who is considered one of the brightest NextGen tennis players. Tennis runs in his blood, as his parents both played tennis for the Soviet Union., His older brother, nicknamed “Mischa,” is also a professional tennis player and is ranked number 30 in the world. After turning professional in 2013, he has continuously been on the rise since proceeding to the semifinals of his first ATP tour event in 2014. In 2015, he broke into the top-100 and made it to his first Grand Slam competition at Wimbledon. He broke into the top-20 the following year. In 2016, he impressed many by competing with many of the top players, defeating his idol Roger Federer, and winning his first ATP title against 2016 US Open Champion Stan Wawrinka. . This year he made even bigger strides by breaking into the top-10 and winning his first ATP Masters tournament (a level below Grand Slams) against Novak Djokovic. His keys to success have been his strong, fast serve and his solid, dependable backhand.

Dominic Thiem

Age: 23
Country: Austria
NextGen: No
Ranking: 8

23-year-old Dominic Thiem of Austria has also been touted as one of the greatest players of this upcoming generation. After choosing to become a pro in 2011, he advanced to his first ATP final and the Fourth Round of the US Open in 2014. Since then, he has worked on his game to become a strong baseliner, using an aggressive one-handed backhand, which is rarely seen in someone so young. In 2015, despite not doing too well at the Grand Slams, he still consistently excelled on the ATP World Tour,, winning three ATP titles through his determination. By ascending in the rankings, Thiem entered a tournament as the top seed and finished the year ranked number 18.. Thiem translated his ATP Tour success to Grand Slams in 2016. A very strong clay court player, he upset then 9-time French Open champion, Rafael Nadal, en route to winning an ATP title on clay. At the French Open, he eventually reached the semifinals of a Grand Slam for the first time, which propelled him to number 7 in the world. In 2017, so far, he has won his eighth ATP title and advanced to his first Masters final. On the clay courts again, he recorded some major upsets by defeating Nadal at the the Rome Masters and demolishing Djokovic at the French Open in straight sets. His aggressiveness, consistency, and strong mentality has made him one of the greatest of his generation.

Milos Raonic

Age: 26
Country: Canadian
NextGen: No
Ranking: 7

The big-serving Canadian known for his philanthropic deeds is also one of the most promising players of his age. Despite being 26-years-old and turning pro nine years ago, he has come into his own in the last couple of years. The Big Four’s dominance overshadowed his achievements when he was in his early 20s, but he has been one of the few players who has slowly narrowed the gap and challenged the sport’s titans. Until 2010, Raonic mainly played in small ATP tournaments and qualified for the Grand Slams occasionally, but lost quite early. However, in 2011, he broke ground when he reached the Fourth Round of the Australian Open as a qualifier, the first to do so since 1999. Many former players praised Raonic, and he backed it up by winning his first ATP title to reach a career high of world number 25. In 2013, he consistently achieved success at many ATP tournaments and broke into the top-10 for the first time. In 2015, he reached the semifinals of a Grand Slam for the first time. Additionally, he reached the ATP World Tour Finals, a tournament where only the top eight players play, and was ranked as high as number four. Last year saw a new Raonic, as he was more consistent and determined than before. His hard work came to fruition when he reached the finals of Wimbledon, and ascended  to world number three. His strong forehand, serve and prowess on all surfaces has allowed him to grow into a strong player who could be the heir to the Big Four.

This year’s Wimbledon brought many surprises and crowned champions new and old at the All England Lawn Tennis and Croquet Club. On the gentlemen’s singles side, Roger Federer cemented his status as the greatest of all time and most certainly the greatest Wimbledon player of all time by winning the tournament and clinching a record 19th Grand Slam title. His 3-set, 6-3, 6-1, 6-4 domination over Marin Čilić secured his record eighth Wimbledon Title, making him the only eight-time champion of the tournament. The man didn’t drop a set the entire way through. On the women’s side, Garbiñe Muguruza won her first Wimbledon singles title at just 23 years of age, defeating veteran female player and five-time Wimbledon champion Venus Williams in straight sets.

On the gentlemen’s doubles side, new champions Łukasz Kubot and Marcelo Melo battled through four five-set matches to win their first Wimbledon doubles title, winning the championship in a thrilling 5-7, 7-5, 7-6, 3-6, 13-11 match against Oliver Marach and Mate Pavic. In women’s doubles, Ekaterina Makarova and Elena Vesnina dispatched Hao-Ching Chan and Monica Niculescu 6-0, 6-0 in just 55 minutes. Although this year unveiled many new champions, Federer’s victory stands above the others as he continues to break records and play some of the best tennis of his career.

Roger Federer’s victory was not entirely surprising, but still left many in the tennis community awed, including himself; Federer described the win as “magical.” Roger, 35, is the oldest man to win the Wimbledon singles title in the Open Era and broke the record of seven Wimbledon titles which he shared with Pete Sampras and William Renshaw. Federer had not won Wimbledon –or any Grand Slam– since 2012 (until this year), seeing his ranking fall to 17 in the world in January 2017 due to a 6-month injury layoff. It was the first time he ranked outside of the Top 10 since October 2002. After Federer broke his Grand Slam title drought in Australia earlier this year, tennis pundits and fellow players knew Federer would be formidable. It was the first time he beat Rafael Nadal at a Grand Slam other than Wimbledon.

In the months leading up to Wimbledon, Federer dominated in two ATP Masters 1000 tournaments. The Masters 1000 circuit, which is just under the Grand Slam tournaments in prestige, had been controlled by Novak Djokovic, Andy Murray and Rafael Nadal for all of 2016, with Federer never even reaching the final of any of the nine tournaments. Then, Federer won the first two Masters of the year by dismantling countryman Stan Wawrinka 6-4, 7-5 in Indian Wells and, again, Rafael Nadal 6-3, 6-4 in Miami.

After taking another break, this time for two and a half months, Federer returned to the ATP World Tour, losing his first match back. However, he quickly quelled rivals’ hopes when he won the Halle Open without dropping a set.

Federer’s return to Wimbledon, however, was flawless. In his first three rounds, he breezed through lower-ranking opponents Alexandr Dolgopolov, Dušan Lajović, and Mischa Zverev. Federer’s Round of 16 match against Grigor Dimitrov foreshadowed a thrilling match against Novak Djokovic in the semifinals and, if he won, against Andy Murray or Rafael Nadal in the finals. But Nadal’s five-set, nearly five-hour loss to Gilles Müller in the Round of 16 seemed to guarantee Murray a place in the final. In the Quarterfinals, more surprises came with Sam Querrey’s stunning five-set upset over Andy Murray. Furthermore, Djokovic, arguably Federer’s toughest competition at Wimbledon, retired to Tomáš Berdych. Federer had lost to Djokovic in the final in both 2014 and 2015; now, with Djokovic gone, it appeared as if Federer had already won the title.

In the semifinals, 2014 US Open champion Marin Čilić regained his composure after losing the first set to Querrey, defeating him in four sets. Federer won in straight sets over Berdych, who was playing extremely well. In fact, Boris Becker, Djokovic’s former coach, commented that Federer had “10 gears” and “whenever he’s in trouble he comes out with an even better shot.” He added that Berdych “played great under pressure,” but Federer’s performance is “what makes him the greatest of all time.” Becker also believed that Čilić would be “dangerous” in the final. After all, Čilić defeated Federer 6-3, 6-4, 6-4 at the 2014 US Open in New York and, last year, forced Federer to battle back from two sets down in a 7-6, 6-4, 3-6, 6-7, 3-6 loss at Wimbledon.

As Federer’s 11th Wimbledon final began, commentators noticed that Čilić looked “tight” early on. Federer’s early break also heightened Čilić’s nerves, who would go on to be plagued by a “huge blister”, and frustration. Federer broke again to secure the first set, 6-3. Federer had not lost a Grand Slam match after winning the first set since 2014, but he and experts knew that Čilić was dangerous. Čilić smashed his racket on his chair during the 6-3, 1-0 changeover, indicating he was mentally unraveling. Federer quickly won the next two games. Now, down 0-3, Čilić began to cry in his chair and some wondered if his slip in the first set hurt him more than he had initially let on. Čilić instilled some hope in his fans when he held serve to make the score 1-3, but ten minutes later Federer won the set 6-1.

In the third set, Čilić stepped up his level of play, but the pressure proved too much at 3-3. Federer secured a necessary break and the held his serve to make it 5-3. Minutes later, Federer was up 6-3, 6-1, 5-4 and 40-30. At championship point, Federer missed his first serve, but nailed a second-serve ace down the middle to secure another Wimbledon title. After the match, Banter Sports writer Nima Majidi said that, “while this year’s Wimbledon tournament was full of upsets, the champion was no surprise. Roger Federer played a great match, and proved why he is the greatest player.”

In the trophy ceremony interview, Čilić admitted, “it was really tough today,” but humbly congratulated Roger for his victory. Federer took the opportunity to congratulate Čilić and assuaged concerns of retirement, saying “I hope I can come back next year to try to defend the title.” Banter Sports Tennis Editor Nikhil Lahiri offered his insight, adding, “Federer seems to be playing the best tennis of his life at the astounding age of 35. He shouldn’t be slowing down anytime soon.”

Federer’s 19th Grand Slam title further extended his lead over other active tennis players. Nadal’s French Open victory last month placed him second with 15 Grand Slams. Meanwhile, Djokovic, who has been not in his best form as of late, trails at 12 Grand Slams. Perhaps Federer’s latest victory is due to the early exits of formidable rivals at this year’s Wimbledon Championships. Even so, his strong performance and consistent execution in matches makes him a dangerous opponent and a player to watch in the upcoming Masters 1000 tournaments in Montreal and Cincinnati and at the US Open, the last Grand Slam of the year. As he rises to 3 in the World, despite starting at 17 in the beginning of the year, many are excited to see if Federer can win more tournaments and perhaps even secure the “No. 1” ranking. Either way, he will surely be celebrating his 8th Wimbledon and his $2.9 million prize.