They have not won a Premier League game since beating Burnley on December 20 and have picked up just two points from their last three games.
But when asked if his side had the qualities to win their survival battle, McCarthy said: "I do believe that we have got it and what you see is what you get from me. I am not any good at acting.
"It is irrelevant what anyone else does and we were never going to stay up on 21 points.
"We are going to have to get near to 40 points. I don't think you will need 40 to stay up but we certainly need another 16, 17, or 18 points.
"But we are capable of doing it and that is what gives me the confidence."
McCarthy has had to rally his players, and himself, in the countdown to the game against Tottenham.
He admits he was left feeling as down as the players by the result at Birmingham when two late goals by Kevin Phillips cancelled out the first-half opener from Kevin Doyle.
But McCarthy has no doubt he will see a positive response against Tottenham.
He added: "After the Birmingham game it was the worst I have felt in a long time.
"But you get better at dealing with that as you get older and I have to go round lifting other people.
"We are all hurting but we have got another game to plan for and we have made sure the players won't take that into this game.
"What we want to do is to take the performance against Birmingham into the game, not the result.
"We did play well. We just need to be more clinical. We could have managed the game better.
"When we were winning 1-0 we could have kept the ball better rather than keep charging forward. But you only learn about the Premier League by playing in it."
Wolves are going for a famous double after winning 1-0 at White Hart Lane in December thanks to a third-minute strike by Doyle.
But McCarthy expects Tottenham to be fired up to make amends for that result and knows his players will have to be at their best to have any chance of taking another three points off Harry Redknapp's side.
McCarthy rates Tottenham highly and said: "Arguably they are a top-four side.
"They will not have enjoyed being beaten by us, that's for sure. I guess revenge would be sweet for them.
"They are a talented team and they have more of a steely edge to them now with Harry Redknapp in charge.
"They play lovely football and that competitive edge makes them a very good side. Everyone can see what a threat they have in attack with Peter Couch and Jermain Defoe.
"We will have to play at our optimum to beat them like we were when we beat them down there.
"Our players left nothing on the pitch and it will have to be the same this time.
We will be the underdogs and punching above our weight and that inspires you as well."