Muggles' Guide to Harry Potter/Characters/Derrick

Peregrine Derrick is mentioned as being one of the Beaters in the Slytherin Quidditch team.

Derrick is one of two Beaters who attempts to injure Harry Potter in the Slytherin / Gryffindor final. (The other is Bole.) He is unsuccessful, being out-maneuvered by Harry.

Angelina Johnson mentions Derrick (and Bole, too) in passing, saying that she always was surprised that Derrick and Bole could make it down to the Quidditch pitch without needing signs.

Angelina's comments indicate that she does not consider Derrick's intellect to be among the strongest. We can't be certain whether this is true judgement or simple inter-house rivalry, but the "traps" he and Bole try to lay for Harry do seem to be relatively easy for Harry to out-think.