Andy Murray conceded he might "need to accept" he is no longer capable of reaching the latter stages at Grand Slams after a demoralising straight-sets loss to Grigor Dimitrov in the US Open second round. The 36-year-old Murray, the 2012 US Open champion, produced a flat display in his 6-3, 6-4, 6-1 defeat to 19th seed Dimitrov, and has not been past the last 32 at a major in six years. "It's obviously disappointing, to not play how you would like, you know," said Murray, who hit 45 unforced errors and just 16 winners Thursday.