Is it a big deal that Novak Djokovic just passed Roger Federer in career earnings?

Roger Federer fans knew the usurper to his crown has been coming for years but only recently realized it'd be Novak Djokovic, not Rafael Nadal, making the push for the honor of being known as the sport's all-time great. But not even the most pessimistic could have seen this happen so fast.

With Sunday's win in the Miami Open, Novak Djokovic passed Roger Federer in career prize money, a development that would have sounded like "Jordan Spieth leaps past Tiger Woods" as recently as a few years ago. But there it is: Djokovic's $1.028 million in winnings put him at $98.2 million for his career, just above Federer's $97.9 million, a figure that hasn't moved since the Australian Open. The leap almost certainly means Djokovic will become tennis's first $100 million man (not that big a deal) while also being the sport's all-time leading earner (pretty big). 

(Photo by Mike Stobe/Getty Images for the USTA)

Or is it? Though Federer and Djokovic will be regarded as contemporaries, and should given that they've played each other 45 times, their age difference (Djokovic will be 29 later this spring, Federer turns 35 this summer) has been a key catalyst in Djokovic's bigger bank account. (On the court, at least. Off the court, Federer still rules with his many endorsements.)

Why? It's the same reason Arnold Palmer can be ranked No. 404 on the PGA career money list behind literally dozens of people you've never heard of. It's why Tommy Robredo has made more money than John McEnroe. It's why the average baseball player will make $4,320,000 more than Babe Ruth did in his prime. Salaries go up. Prize money goes up. Sports is like the stock market, only you never need to tough it out through a bear market.

But comparing Bryce Harper and Mike Trout with Babe Ruth is an obvious apples and oranges situation. It's no surprise that baseball, basketball or football players, or anyone really, makes more money than athletes of a past generation. But Federer and Djokovic are ostensibly from the same era. What gives?

(Photo by Yunus Kaymaz/Anadolu Agency/Getty Images)

Here's where that six-year age gap comes in. Federer and Djokovic make a bulk of their prize money at Grand Slams and Masters 1000 events, the latter of which has been called three different things in Federer's 18 years on Tour. While Djokovic has a few more Masters titles, Federer still dominates in the more-profitable Slams and that's where this era-bias reveals itself. Here are the career stats at finals in both types of events for both players (since finals are where they make their real money):

Federer: 17-10 in Grand Slams; 24-18 in Masters 1000

Djokovic: 11-8 in Grand Slams; 28-12 in Masters 1000

(AFP/AFP/Getty Images)

By those numbers, Federer should be ahead of his "contemporary," if not by a huge margin than a substantial one, no? He has 27 total Grand Slam finals and 42 Masters finals against 19 and 40 for Djokovic. But the game has seen such rapid financial growth during that time that comparing the two, while not quite like Tiger and Arnie, is frivolous.

Consider of Federer: 16 of his Slams wins came more than six years ago. Djokovic was won 10 since then. Federer won 21 Masters before the 2012 U.S. Open and only three since. Djokovic has won 16. 

Just because of you're of the same era doesn't mean you're of the same prime.

When Roger Federer won the 2004 U.S. Open, which was the year of his first three-major season, he took home $1 million. By 2014 the prize money had tripled and in 2015 Djokovic won $3.3 million. In 2005, Federer beat Andy Roddick for his third-straight Wimbledon title and won $1.1 million for the effort. A decade later when Djokovic beat Federer, the Serb brought in about $3 million American dollars. The game done changed.

(Photo by Clive Brunskill/Getty Images)

So in a few years, when Djokovic begins his decline and Federer is out of the sport, the debate will turn to the G.O.A.T., as it always does in tennis. (That is, unless Djokovic happens to win 10 of the next 14 majors to put it out of reach - which isn't happening; they all hit the wall one day.) And though prize money might seem like a good barometer for two men who will likely end up playing more than 50 times, the economics of tennis has changed so much that Djokovic has often been getting $3 dollars in his his prime to every dollar Roger Federer got. 

There's going to be so many different ways to rank the two players as time goes on. Earnings won't be one of them.