It had been felt that the England international defender, who is nearly 33 and has been plagued by fitness problems for three years, might be being eased out at Old Trafford.
With that backdrop, it is not a surprise that ambitious MLS outfit
"It has been a very frustrating period for all concerned Moralee told Press Association Sport.
"What he wants to do is put his injuries behind him and start showing the form that even last season he produced against some of the very best forwards in the world.
"Rio understands there is some great talent at Manchester United. But he is up for the challenge of that and I am sure he has a big part to play.
"He is now in his 10th season at United. He still has a great hunger and desire to win trophies. It is the type of challenge he thrives on."
"I understand the reasons why someone like Rio would be attractive to them," added Moralee.
"There is an appeal on and off the pitch because he could help retain the global status provided by Beckham and Henry.
"But I must stress, these stories are nothing to do with Rio.
"We have never discussed anything beyond life at Manchester United because that is all he cares about."