Mothiba has hit the ground running at French club Strasbourg following his recent R135m signing from Lille, netting five goals in eight appearances for the Ligue One side.
The big 22-year-old also curled home a superb shot when Bafana demolished Seychelles 6-0 in the AFCON qualifiers during the FIFA break to make it three goals in four international appearances.
McCarthy, who also burst onto the scene as a youngster during his playing days, is pleased by Mothiba's progress.
"He just has to keep going and I think at the rate that he is going he might find himself moving again from his club very soon," McCarthy tells KickOff.com.
"He's got a big move in him. I think he's very Shaun Bartlett-like in terms of his stature. He's very quick, strong, and he's just doing what he's doing and been exceptional. Soon he'll be the answer for the national team.
"We have just got to try and keep him as fit as possible, no injuries. Listen, he's doing all the right things and he just has to continue what he is doing; keep his head down, feet on the ground. Every game he has to come out off the bench and do exactly what he did against Monaco.
"I'm very proud to be watching him," concludes Bafana's record scorer with 31 goals and the only South African to win the UEFA Champions League.
Mothiba, a former Mamelodi Sundowns academy player, initially joined Lille in 2014 from the Benoni-based Diambers Academy.