The Japanese trailblazer once again suffered fitness issues throughout 2016, hampering a promising campaign that included a second career Masters final in Miami and a US Open semi-final appearance that included quarter-final victory over Andy Murray.
Having lost to Stan Wawrinka in the last four at Flushing Meadow, the former world No 5 also made the semi-finals for the second time at the World Tour Finals but at 27-years-old he now needs to make his mark at the top level.
He began the year with defeat to Grigor Dimitrov in the final of Brisbane, while in Melbourne, Nishikori was beaten in a five-set thriller to eventual champion Roger Federer.
His best Grand Slam result remains a 2014 runners-up spot at the US Open, where he beat Djokovic in the semi-finals before losing in straight sets in the final to Marin Cilic.
Nishikori is yet to go beyond the fourth round at Wimbledon, a record he will look to amend this July.