Nike's losing major ground. Fed and Nadal are not going to be in many more major finals which is the most exposure for the brands. Also, Nike's investments in the next wave - Dimitrov, Harrison and Tomic has so far not paid off, or even come close.
Expect Nike to make a big push for Djokovic.
"Rather than love, than money, than fame, give me the truth." --Henry David Thoreau