2015 : The transition to complete aggression:
Federer had brought in extra aggression and serve reliance in 2014,Which had led to substantial improvement in results.It was only logical to follow that path.Fred,being,a purist and a fan of 90s playstyle,employed even more net play in his matches.He began to take more risks on return and started trying to rush his opponents even more.This basically included trying to take the initiative at any possible instant and rushing the net or trying to hit a winner.This style was extremely difficult to pull of and the execution had to be perfect.But Federer is crazy talented.He not only executed his style of play perfectly,he exposed the current players unease against constant and intelligent aggression.He was a delight to watch,bringing back the nostalgic memories of the 80s and 90s.
But the problem was this was not 90s.Even an outrageous volley winner after exceptional net coverage won you just one point and the question was no matter how talented you were,the difficulty level meant you were not going to keep doing it.
The major flaw in his game was that even though he was applying several tactics,his overall game plan was limited and lacked substance, it was too focused on shortening the points.His aggressive play meant that many times he was going for meaningless net exploits,ignoring percentage play and on the whole having a very low margin for error.His style was superficial and suicidal ,this spelt disaster in best of 5 sets where it was hard to blitz a good opponent.Avoiding baseline in the era of baseliners was a huge mistake.An aggressive player without a stable baseline weapon was not going to win a Grand Slam in 2010s.Somebody with enough balance in his game and patience with ability to make Federer play on his own terms, was going to figure this out.Admittedly such a player had to be an all time great himself.Unfortunately there was a certain ATG around then: Novak Djokovic.
The solution to the problem,Giving 2015 aggressive mindset the correct expression:Sustained baseline aggression with a stable weapon.
Now that he knew that as great his 2015 approach was he was not winning slams with it.
This is where Ivan and the backhand idea steps in.His coaching team learned from the mistakes and successes of the past 2 years and chose to make his now more stable backhand a weapon.He cut down his unnecessary net rush in favour of more meaningful baseline point construction,being aggressive and taking the ball early from the baseline meant the same effect (rushing his opponents and taking the their time away)as his previous style but now it was safer without the previous risks of being passed and taking the wrong initiative from the get go.
Now he had a weapon a rely on,a stable baseline game and moreover the alternative of taking the same approach as 2015.This new depth in his game has made him successful at this age.
Most importantly,the failed and sometimes idiotic attempts at aggressive returning in 2014-15 which lost him many B.Ps,had a positive effect as he learned from his mistakes and improved his return to lethal level.