The 23-year-old Brazilian defender joined the Reds from the Portuguese giants on deadline day and has made two substitute appearances for the club so far this season.
Morato played 86 times for Benfica but was far down in the pecking order at the club as Costa spoke about why he was eventually sold on.
“Two years ago, Morato had a different projection, but we didn’t want to devalue the resource and damage the player’s career by keeping him as a fourth centre-back.
“He probably would have had a few minutes during the season, so he left. We kept the three centre-backs, plus one from the youth team.”
Morato has not earnt his place in the Forest team as of yet but will be looking to make his way into the starting eleven ahead of Nikola Milenkovic and Murillo.