De Gea, meanwhile, was on the verge of making the opposite move to Real Madrid in the summer of 2015 before the transfer collapsed on deadline day after paperwork failed to arrive at La Liga headquarters in time.
Mourinho indicated Morata had been one of United's top targets as the club prepares to return to the Champions League, but no agreement could be reached with Madrid.
Speaking in the mixed zone after United began their preseason tour of the United States with Saturday's 5-2 victory over LA Galaxy, Herrera said the speculation over De Gea's future was getting repetitive.
Morata is now sick of not being a guaranteed starter, sick of not playing 45 or 50 matches a year. I cannot criticise Real Madrid and I can not criticise my club.
He continued: 'He's happy and I know this is going to sound repetitive because I always say the same by David is one of the few keepers who wins you points.
But Mata still thinks "things can happen" with United and Morata.
Liu Xiaobo's body cremated in private ceremony
Authorities have tightly controlled information about Liu Xiaobo's health and life as well as access to his family members. He said he admired Mr Liu's courage, and believes he should have been allowed to leave China.
The Spanish striker was very close to joining Manchester United earlier in the summer transfer window.
"It is a right of Madrid to ask for their players the amount they want".
De Gea, too, enjoyed a solid season for Manchester United, particularly in the Premier League as he kept 14 clean sheets in 35 matches while conceding just 29 goals.
If De Gea was anywhere near leaving the Reds for a life back in Spain, Mourinho would still be comfortable with the dependable Sergio Romero, who stood out with the opportunities last season. "He is going to stay".