Ander Herrera has defended manager Jose Mourinho and argued Manchester United’s players share his sense of frustration at the way the club’s tour of the USA has unfolded.

Mourinho’s increasingly erratic behaviour has unsettled some members of his squad, with sources revealing they feel they are treading on egg shells less than two weeks before the start of the Premier League campaign.

The Portuguese’s relationship with striker Anthony Martial appears to have broken down completely after the Frenchman left the tour early to attend the birth of his son in Paris, only to then fail to return.

Yet Herrera insisted Mourinho’s combative approach is what the players need and described his battle to sign more players this summer as a normal one between a manager and his employers.

“First of all, I have to respect what my manager said, because he knows what he's talking about,” said Herrera.

“Secondly, I am a football player. My work is on the pitch, not in the office. The other things, they are too far from my hands. So, I think we have fantastic players, but, of course, always managers want to improve their teams, but it’s not my business. It's something between the manager and the club.