David Beckham's troublesome ankle injury led to the midfielder sitting out Los Angeles Galaxy's 1-0 defeat by New England Revolution.
Beckham, 32, who was not even named among the substitutes, watched as Taylor Twellman scored the only goal.
"I'm always disappointed when I can't play but I'm working hard so I'll be able to play again soon," said Beckham.
He expects to be selected for England's friendly against Germany on 22 August, even if he is not fit to play.
England boss Steve McClaren watched as Beckham made his Major League Soccer debut on Thursday, coming on for the final 18 minutes of Galaxy's 1-0 defeat by DC United.
606: DEBATE
The former England captain said: "I spoke to Steve about my fitness and how it has been over here.
"He said he is looking forward to me coming over, even if I can't play. It is important that all the players are together.
"It is good to get together as a team, so hopefully I can be there but I have to be fit physically and mentally to play for my country and I have to play for the Galaxy first."
Galaxy coach Frank Yallop admitted Beckham's cameo against DC United had "set him back", while the flight from Washington to LA had caused more swelling to his ankle.
But Yallop remains hopeful that Beckham will play some part in the Galaxy's next match - at home against DC United in the SuperLiga on Wednesday.
"We're hoping that having a day off today will make it better for Wednesday, so we'll see," said Yallop.
"We are flying again tonight and hopefully by Tuesday morning he will feel a lot better."
~RS~q~RS~~RS~z~RS~21~RS~)