Niasse joined Everton from Russian side Lokomotiv Moscow in a £13.5million deal on transfer deadline day.
“Oumar has got a really good physicality – he is very strong and powerful,” said Martinez.
“It’s not just scoring goals… he can open up teams in the final third.
“He is going to be a terrific, fresh addition.”
Niasse became the third most expensive signing in Everton’s history.