Toffees manager Roberto Martinez revealed on Tuesday that a deal had been agreed with Chelsea, and McCarthy believes that Atsu will be important for the club this season.
"I don't know much about him, but I've seen wee clips here and there," the midfielder told the Liverpool Echo. "The gaffer has scouted him for a while, and I'm sure he'll be a good addition to the squad with so many games coming up this season.
"He has a bit of impact and a lot of pace about him from what I've seen."
Atsu moved to Chelsea from Porto last summer, but is yet to make a competitive appearance for the club.