It is the Belgian coach's first game in charge since signing a four-year deal with the North Africans last month.
Gerets says Chamakh has improved considerably since joining Arsene Wenger's team from French club, Bordeaux.
The 26-year-old moved has made a fine start to life as a Gunner, scoring eight times.
Gerets said: "When he played in France he was very good in the box and scored a lot of goals with his head.
"But I get the impression since he has joined Arsenal he has become a more complete player.
"They play fantastic one-touch football and he is getting better every week as he gets used to this new kind of play.
"He is doing a great job for Arsenal. It is not easy to change your game but he is doing very well."
The 56-year-old Gerets has been charged with the task of reviving Morocco, who have under-achieved in international tournaments over the past decade.
"I think there is a big potential," said Gerets, who has also coached Turkish giants Galatasaray and was last in charge of Saudi Arabian club Al Hilal.
"They have a lot of good players. For one reason or another they have not been successful in the last couple of years but I think we can change this."