Actually, Nick's lack of brightness might help him against Novak: He might be too stupid to realize he's playing Novak and should lose
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As for the "weak eras" argument, I was actually fiddling about with a blog about this, comparing Novak's unparalleled dominance over the last year and half to Roger's best years. I actually think the tour has been weaker over the last year and a half than it ever was under Roger, with the possible exception of 2004. But by 2005 Rafa was playing at a very high level and dominating clay, and Novak started getting good in 2007.
But more so, as I said in another thread, the second tier talent of Roger's generation was stronger than the second tier talent today. Safin, Roddick, Hewitt, Nalbandian, Davydenko, Ferrero, etc...these guys were more competitive than the group of second tier today: Ferrer, Tsonga, Berdych, Cilic, Gasquet, etc.
Actually, it seems that a lot of really dominant years in tennis history weren't only about a great player destroying everyone, but other factors - maybe an injury or decline from other top players, a change in generations, etc. Even looking at Rafa's best years--who had the misfortunate of his peak overlapping with Roger and Novak--you can see some of this: in 2013, Roger was AWOL, and there was only really Novak and Andy to contend with. In 2010, Novak was struggling, Andy was Andy, and Roger was in decline. In 2008, Roger was dealing with mono, Andy and Novak were just getting good.
When you have years where several top players are in peak form you get something like 2012, the Year of the Big Four.
But where Roger and Novak are similar is that they combined a couple major factors: a very high level of talent across all surfaces and amazing health and the resulting consistency. This allowed them to take advantage of the weaknesses of lesser players and dominate the way Roger did and Novak is. Not every great player can do this.