You cannot use the highs and lows of a career as proof of a radical difference. Once again, Djoko beat Fed in 2 different slams BEFORE 2011. Why on earth shouldn't that count??? If he hadn't beaten Fed in a slam before 2011, then you would have a point, but he did, twice. So regardless of his career tribulations, no magical transformation actually happened in 2011 in that department (and even when Djoko ended up not beating the big names in slams pre-2011, there is no way you could claim that he was not perceived as a threat).