Why 2019 could finally be the year of the Big Four's demise

Novak Djokovic's status as the man to beat in 2019 is indisputable. But when it comes to those other men who have long dominated their peers in the ATP -- Roger Federer, Rafael Nadal, Andy Murray and Stan Wawrinka -- things are not as clear. In fact, they're murkier than they've been since the unit known as the Big Four began to dominate major events.

Unless Djokovic runs the table, chances are strong that the Grand Slams will produce a winner outside the usual suspects for the first time since Marin Cilic won the 2014 US Open. There's been a lot of chatter at the end of the year about the up-and-coming #NextGen players, led by recent ATP Finals champion Alexander Zverev. But the outsider most likely to crash the Big Four + Stan party probably will be one of three seasoned, tenacious, over-30 veterans.

Two of these contenders have tasted Grand Slam ambrosia in what amounts, at least in tennis time, to the distant past. Neither has given up on the dream. The three have moved as a group in 2018, inching up to finish ranked Nos. 5, 6 and 7. Most importantly, they are cut from the same cloth; they are big (between 6-foot-6 and 6-8), rangy, powerful and experienced. Let's take closer look at each of them:

Juan Martin del Potro

Ranking: No. 5
2018 record: 47-13, two titles, including the Indian Wells Masters

Time and again, the 6-foot-6 Argentinian has come close to securing that second Grand Slam title to put a crowning touch on his remarkable comeback. Debilitating wrist injuries and three surgeries almost ended his career soon after he won the 2009 US Open at age 20, but he has fought his way back to the highest level of the game.

Beloved for his introverted, calm temperament as much his inspirational tale of resurgence, Del Potro hit a career-high ranking of No. 3 in mid-August. But just weeks later, after he lost the US Open final to Djokovic. Del Potro's career once again came to a grinding halt, though, as he fractured a patella in Shanghai and was forced to quit for the year.

"I felt like the world fell apart," he later wrote on a post on Twitter. "I had to change my goals because of this."

It's unclear if Del Potro, 30, will be ready for the start of the new year. But if his knee heals well, the premature end to his career-year might prove a blessing in disguise. His surgically repaired wrists were showing signs of overuse as 2018 went on, so the rest might do them good. Del Potro had to rely on a one-handed slice backhand through most of his comeback, but this year he was able to work that more potent two-hander into the mix more freely. The result is a more well-rounded ground game, grounded in that whopper of a serve.

"It's a fight against bad thoughts," Del Potro wrote of his latest rehab cycle. "But be sure that I am willing to keep on playing even if it is not easy."

Del Potro mastered Federer in the Indian Wells final, ending the Swiss' 17-match winning streak at the start of 2018. It lifted his record against Federer in finals to 4-2.

Kevin Anderson

Ranking: No. 6
2018 record: 47-19, two titles

The oldest (32) as well as the tallest (6-foot-8), Anderson is the only player in this trio never to have won a major. But he's a late bloomer who conquered early career confidence problems and enjoyed a big year in 2018. While he has just five career titles (none of them a Masters grade or better), Anderson convinced himself that he belongs among the elite. At Wimbledon his game -- and grit -- added credibility to his opinion.

Anderson's quarterfinal clash against Federer was a highlight of the year. The challenger coolly stared down a match point and eliminated the defending champion in overtime, 13-11 in the fifth. Anderson had no won as much as a set against Federer in four previous meetings.

"Even if the matches have been maybe sometimes one-sided, you always know he can pick it up," Federer said of the raw-boned, hard-serving South African. "All of a sudden you won't see breaks for some time."

Anderson followed up that win with an epic performance against John Isner, in the match that finally persuaded Wimbledon to adopt a fifth-set tiebreaker. Fighting off fatigue, Anderson advanced, 26-24 in the fifth. But he was running in fumes in the final, a straight-sets loss to Djokovic.

At the ATP Finals, Anderson survived the round-robin stage to reach the semifinals in his debut. He's evolved into one of those hard-working, easily overlooked, highly focused players who is bound and determined to get what he wants: a major.

Marin Cilic

Ranking: No. 7
2018 record: 44-20, one title

It will be five years next September since Cilic cracked the Grand Slam code to win at Flushing Meadows, despite the hegemony of the Big Four. Roughly a year and a half ago, he reached the Wimbledon final, but realizing he had no chance against Federer, Cilic, as the match was coming to a conclusion, sat in his changeover chair with face stained by tears of frustration and anxiety. Cilic did not fare much better this past January when he was thumped in the Aussie Open final, against Federer again.

Paul Annacone, a Tennis Channel analyst who has coached Pete Sampras and Federer, told ESPN.com that Cilic "is the guy none of the big players like to see across the net, not with those weapons, not when he trusts himself."

The problem has always been that at big moments against top players, Cilic has had a tendency to dial back his game just that wee bit instead of cranking it up. It has made all the difference. "The second serve becomes not quite as big," Annacone said. "His groundstrokes get a little more erratic."

Cilic, though, is the most well-rounded of this dangerous trio. He moves extremely well for someone who's 6-foot-6, and attacks with skill. Cilic's serve can jar an opponent's fillings loose. But then, Del Potro and Anderson are equally adept at smoking opponents -- or each other. And that just might be what Djokovic & Co. are hoping they will do, because taking down more than one of the game's elite in succession at a tournament is pretty much a lost cause.