The new boss brought Smith into his side for the first time when Burnley visited prior to New Zealand’s match against China last week and McCarthy, a central defender in his playing days, was impressed by what he saw.
“I thought he got better and better in the game,” he says.
“When he started he looked like he’d been out and he was playing against Charlie Austin, who pulled it down and won a few headers but then he never had a kick after that. I thought Tommy played well.”
He says Smith has benefited from having veteran Danny Higginbotham next to him to learn from.
“It’s nice to have that experience alongside him without any doubt.”
The 22-year-old missed most of last week’s trainings with the Championship side as he was in China skippering the All Whites to a 1-1 draw in the FIFA international window.
Despite the inconvenience, McCarthy has resigned himself to having to contend with the centre back’s regular round-the-world treks to represent his country.
“I can’t do anything about that,” McCarthy says.
“I don’t get wrapped up in all of it. That’s the way it is and we’ll have to manage it.”
After sitting out Saturday’s 6-0 hammering at Leicester City, Smith could be in line for a return when Peterborough visit Portman Road on Saturday.
McCarthy and his men will be desperate to pick up three points as they currently lie third from bottom in the 24-team Championship.