Foster became the most expensive player in South African history in January when the Clarets paid a reported €7m fee to snatch him from Belgian side Westerlo.
That record had previously been held by McCarthy after the former Blackburn Rovers man was signed by Celta Vigo from Ajax in 1999 for €6m.
McCarthy, who now coaches at Manchester United, has revealed he’s already spoken to Foster to give him some advice ahead of his first season in the top flight.
“I was just wishing him all the best and I just told him to prepare himself properly because he’s going to be on the biggest stage in the world in the Premier League,” he told South African publication Marawa Sports Worldwide.
“And every opportunity, whether it’s half an hour, whether it’s five minutes, 10 minutes, the whole world will be watching him.