Former World No.1 Andy Murray scripted a fine comeback from a set down to upset Denis Shapovalov in the first round of the Dubai Tennis Championships, but said he "probably doesn`t have too long left" in his career.

Murray refused to be written off and held firm for a three-set win 4-6, 7-6(5), 6-3 against Canada`s Shapovalov to seal his 500th tour-level victory on a hard court.