So Federer is trash? I don't like Fed, but he is certainly no loser. 2014-2016 Fed was quite aggressive, and 2017 Fed has been more tactical. He knows he can't keep this up for much longer.
Nadal's form took a dive in 2015-2016, but has been resurgent in 2017 so far. Sub-par Nadal won 5 titles total in 2015 and 2016. Sub-par would be making 6 or so finals, but winning 1 or 2 finals at most.
Even a fit Murray lost to Djokovic on most matches from 2015-2016. He did beat Novak in Rome 2016 and WTF 2016. Not necessarily a pigeon, but it did take him the whole of 2014 to recover. 2015 Murray was physical, but his mental game was pretty bad.