In the early days of Djokovic's partnership with Uniqlo in 2012, the Big Four (Federer, Nadal, Djokovic, Murray) was at its peak, trading Slam wins as Djokovic failed to build on his monstrous 2011 season. He finished 2012 as the year end world number 1, and won the 2013 Australian Open a few months later
However, between 2012 and 2014, Djokovic's record in Slam finals was poor, as he lost 5 out of 6 finals, including the US Open 2012 and Wimbledon 2013 finals to Andy Murray, and the French Open 2012 and 2014, and US Open 2013 finals to Rafael Nadal. Questions were being asked of Djokovic's mental strength in big matches
Djokovic answered his critics in emphatic style, winning the Wimbledon 2014 final in a classic against Roger Federer, before completing the non-calendar Grand Slam by winning all four slams in a row between Wimbledon 2015 and French Open 2016, a feat only matched by Rod Laver. He was now firmly in the 'Greatest of all Time' discussions
