Carrick was carried off on a stretcher in England's 2-0 defeat to Spain with an ankle injury and Martial limped out of Wembley on crutches following France's loss to Roy Hodgson's side on Tuesday.
There were fears Martial would be set for a lengthy spell on the sidelines, but Van Gaal delivered some positive news regarding the 19-year-old on Friday.
The United manager said Martial would miss Saturday's match at Watford.
But when asked how long the Frenchman would be out for, Van Gaal said: "Not so long, it's a matter of time."
On Carrick, Van Gaal said: "It's not a heavy injury so he shall play much quicker than everybody has written."
There was some bad news regarding captain Wayne Rooney, who is likely to miss the game through illness.
"Wayne Rooney was also ill after the international break," Van Gaal said.
"I only saw him the day after he played then he was at home yesterday so I think he can't play."
Rooney's absence means Van Gaal is desperately short of attacking options for the game at Vicarage Road on Saturday lunchtime.
United's only other striker James Wilson is lacking fitness while Marouane Fellaini, who has played up front for Van Gaal, is unavailable due to a calf problem.
"Wilson can play but he cannot play a whole match because he doesn't have the rhythm of the game," Van Gaal told MUTV.
Antonio Valencia (foot) and Luke Shaw (leg) are also out through injury.
Martial, Morgan Schneiderlin and Bastian Schweinsteiger were all involved in France's victory over Germany that was targeted by terrorists.
Three suicide bombers blew themselves up outside the Stade de France during the friendly, but the match went on.
Further attacks occurred in the French capital on Friday night and 129 people were killed.
Van Gaal has spoken to the three players who were involved in the friendly and will check upon them again before deciding whether to field them at Watford.
"What they have told me is private I think, but we have communicated about it (the attacks)," Van Gaal said.
"I think it is, for every human being in this world, a big blow, so I don't think I have to mention what our discussions were.
"Schweinsteiger and Schneiderlin can play, if we don't take into account this event that has happened."
Van Gaal has backed the Premier League's decision to play the French national anthem before every game.
The Dutchman said: "We, as a member of the sport of football, we cannot do too much.
"But we can give support in symbols, and I think this is a nice thing for the French people, the victims and the relatives of the victims.
"I think it can give them force and strength to survive."
Source : PA
Source: PA