Murray suffers his worst defeat ( in terms of rankings ) since succumbing to world No. 51 Juan Ignacio Chela at the 2006 Australian Open .
Murray has hit back at critics of his latest performance .
Suffering his worst defeat ( in terms of rankings ) since succumbing to world No. 51 Juan Ignacio Chela at the 2006 Australian Open , Murray has hit back at critics of his latest performance .