After their draw in Japan on Friday, United will fly to Hong Kong on Saturday expecting to take on local side Kitchee FC in the final game of their five-match tour of the Far East and Australia.
Yet they have no idea what conditions they are going to encounter.
Tottenham manager Andre Villas-Boas has already voiced his concern ahead of his side's second game at the stadium against South China on Saturday, with Jan Vertonghen having injured ankle ligaments in Spurs' game against Sunderland on Wednesday.
Moyes has seen the pictures from the opening round of matches in the Premier League Asia Cup and with reports that the rain is due to last until Monday, there is a fear about how much damage players could sustain on the surface.
Press Association Sport understands senior figures at the club have even examined the contract for the game to see what contingencies are in place for such a situation.
However, with contractual obligations to meet, there is no question of a postponement at the present time.
Nevertheless, Moyes is worried.
"I do have concerns about the surface," he said.
"It is mainly due to the weather. That is an act of God. We can't do anything about that.
"But we will travel to Hong Kong and hope the conditions improve and the pitch is in a better state than it has been in recently."
Meanwhile, Moyes confirmed midfielder Shinji Kagawa would not fly to Hong Kong.
The Japan star cut short his holiday in order to feature in both pre-season matches in his homeland.
But Moyes feels Kagawa still needs to complete his break after featuring in the Confederations Cup in Brazil.
"We have given him more holiday because of his football with Japan in the summer," said Moyes.
"We try to give all the players four weeks' holiday if possible.
"He hasn't quite had that time so we will give him another week's rest, although he will do some more training with the club here so he can have that time at home in Japan."