Every tennis fan has heard the argument. Roger Federer, his critics say, holds 17 major singles titles, the all-time record, only because he's part of a "weak era."

Here's the theory: Federer racked up 12 of those 17 Grand Slam championships between 2003 and 2007, when his chief competition was unusually raggedy. His generation's top stars, after Federer himself, were the middling champions Lleyton Hewitt, Marat Safin, Juan Carlos Ferrero, David Nalbandian, Tommy Haas, Nikolay Davydenko, Andy Roddick and Fernando Gonzales.

Rafael Nadal, more than four years younger than Federer, kept the Swiss from winning everything in sight during those years by reaching a high level of play early in his career, scoring his first French Open championship in 2005 at 19. By 2008, Nadal had reached his prime and taken Federer's Wimbledon title and his number-one ranking. Soon, Novak Djokovic, nearly six years younger than Federer, had also surpassed the Swiss, proving once again that Federer wasn't all that the late David Foster Wallace had made him out to be.

The theory keeps coming up on social media and elsewhere, what with Djokovic now more than halfway to Federer's Grand Slam total, and that might lead one to think that where there's smoke there's fire. But the thing is, if you buy into the Federer-had-it-easy reasoning, then you have to say that Djokovic, the reigning Wimbledon champion and World No. 1, is also benefiting from a weak era -- perhaps one that's even weaker than Federer's. Djokovic has won eight of his nine majors in the past five years -- which, quality-wise, has clearly been a fallow period on the tour, right? The Serb has faced Federer, a guy well past his 30^th birthday, in the last two Wimbledon finals. His natural rival, Nadal, has struggled with chronic injury problems for years and has now fallen to 10^th in the world rankings. His other natural rival, Andy Murray, beat Nole in two major finals in 2012-13. The Scotsman then had his own injury issues that took him a year to shake off. In the past year-and-a-half, Djokovic has lost twice at majors to 30-year-old Stan Wawrinka, whose overall career highlights still fall comfortably short of Lleyton Hewitt's. And finally, unlike Federer, Nole has had nothing to fear from the next generation, which so far has failed to deliver a breakthrough star.

OK, in case it's not absolutely clear, let's state it baldly: the arguments expressed above are ridiculous. Complete poppycock. As this column has stated before, there is no such thing as a weak era in professional tournament tennis and there never will be. It's as mythical as the Loch Ness Monster. There's too much money and prestige and fame involved for a weak era to be possible.

The fact is, in the early 2000s Lleyton Hewitt was the most fearsome competitor since the young Jimmy Connors, and Marat Safin was the most powerful groundstroker the sport had ever seen. These days, it's strange to see Wawrinka winning majors, but not because he isn't a great player. It's because for a long time Federer, Nadal and Djokovic -- as well as guys like Jo-Wilfried Tsonga and Nicolas Almagro, who've both beaten him at majors -- managed to keep him down. And the next generation -- from Grigor Dimitrov to Nick Kyrgios -- hasn't risen up yet not because they lack the talent and ambition of the current kings. It's simply that it is very difficult to break through against determined elders, as Djokovic found out in 2007-2010 -- and as Andre Agassi, to name just one earlier champion, found out in 1988-91.

After the 33-year-old Federer impressively ousted Andy Murray in the Wimbledon semifinals last week, former champion and current commentator John McEnroe admitted he'd erred a couple of years ago when he declared that Nadal had surpassed Federer as the greatest tennis player of all time. "I was wrong," he said.

Well, he was and he wasn't. Any time you declare the greatest player of all time you're ultimately going to be wrong. Every generation provides us with a new greatest player ever (occasionally more than one), which doesn't mean the present greatest is greater than those who came before. Because each generation stands on its own.

Federer, Nadal and Djokovic have all earned greatest of all time status, joining Rod Laver and Bjorn Borg and McEnroe, among others who were declared the greatest of all time before them.

-- Douglas Perry