Midfielders could miss out on 25-man squad...
Top-flight clubs will have to name a 25-man squad at the end of the summer transfer window, including eight players who are classed as home grown, and the squad list cannot be renewed until January 1.
Hargreaves has had trouble with knee injuries at Old Trafford since joining from Bayern Munich in 2007, while Anderson is not expected back until late September due to a cruciate ligament injury.
Ferguson told Press Association Sport: "It does give me a problem, but I have just got to wait as long as I can.
"I have to make a decision at some point of course and it depends on when I think those players can come back.
"Most of it [the squad] is formulated in my mind, but one or two I have to make decisions on."
Summer signing Javier Hernandez has joined up with the squad for the first time in America following an extended break after the World Cup and could make his debut against the MLS All-Stars.
"We need to assess what he has been doing physically in the last week or so," Ferguson said.
"We would like him to play a part in the game because there is a big Mexican population in Houston.
"We want to try and integrate him into the team as quickly as possible but we need to have a chat with him first."