Jamie Murray believes brother Andy needs to "let his guard down a bit" if he is to take his game to the next level.
Andy Murray's form has slumped since his trouncing by Novak Djokovic in the final of the Australian Open in January and he bowed out in the first round for a third successive tournament with defeat by Alex Bogomolov Jnr at the Sony Ericsson Open in Miami on Friday.
That loss was the world number four's second in a row to a player ranked outside the top 100 bringing further spotlight on his coaching staff.
Alex Corretja and Dani Vallverdu, in addition to mother Judy Murray, comprise the Scot's support team at tournaments, but there is a growing feeling that Murray needs to appoint a full-time coach, with eight-time grand slam winner Ivan Lendl this week touted as a possible candidate.
And Jamie Murray concedes it is time for his brother to employ the "right person" if he is to realise his dream of becoming a grand slam champion.
"Andy could do with some advice from the right person," Jamie Murray told The Times.
"He is good enough to get to that next level, but he needs that something extra that's missing. He needs to find it from himself more than someone else.
"It's a mental thing, he has all the ability in the world.
"Maybe it's his approach to tennis. If he does go a different route, you have to give your trust to that person. You have to let your guard down a bit, listen to the guy and accept he's giving his opinion."