The midfielder completed a £9 million move to Goodison Park from Manchester United on summer transfer deadline day.
However, Garner had a substitute cameo for England under-21s against Italy before featuring for 70 minutes - and impressing - in a 3-1 defeat of Germany on Tuesday night.
Carsley admitted he had been worried about Garner’s condition heading into the camp.
But the young Lions chief and ex-Everton favourite was highly impressed by the former Nottingham Forest loanee’s fitness and performance.
What’s been said
Speaking to The Athletic, Carsley said: “James did really well.
“You always worry when players have a lack of minutes but he came into camp in really good condition.
“Hopefully, Everton will have watched him and he’ll have put himself in a better position (to play more regularly).
“He’s an all-round box-to-box midfielder. He can play a variety of roles and has a lot of attributes.
“If you can be mobile, get around the pitch and play six as well then it really helps because of the ground you can cover.”
Garner is expected to be in Everton’s squad when they travel to Southampton on Saturday.