Forest brought in an English record 21 players in a single transfer window following their return to the top flight, before signing free agents Serge Aurier and Adnan Kanuric in September.
Cooper told the BBC on Monday that he did not want to be overly critical of his side just eight games into the season.
"Without sounding too soft, it is really difficult to be too critical of the group because it is a completely new group and we are finding out about ourselves, the job," he said.
"They are just a really fresh group trying to come together. We are going through difficult moments you normally look at in pre-season and we are having to go through that process it in the most difficult league in the world.
"Some of the guys have only met each other these last couple of weeks. That's the realism of the situation and something we have to deal with. At the moment we are getting punished because of periods in games where we are not a team and key moments as well."
Forest, who have lost five straight games, next host Aston Villa on October 10.
