The players were given a special programme – designed by former England midfielder Tony Daley – to follow during the close season.
McCarthy said: “They’re all looking remarkably fit. Tony has been excellent in setting them programmes in terms of fitness, strength and conditioning.
“They have all adhered to them. They know they have to because they can’t come back and be behind.
“In the old days they used to run you until you were sick – and if you were sick you weren’t fit enough so they ran you some more.
“That approach is old money now.”