Wolves returned to winning ways with a 3-2 victory at Watford over the weekend but the boss remains concerned with what he describes as a 'sieve like defence' that has leaked 14 goals in the last five games.
McCarthy fumed: "I lambasted the players afterwards - I gave them the sharp end of my tongue because we shouldn't have made it so difficult for ourselves.
"We're a sieve at the back and we have to change that. Either we defend better individually or collectively or we'll have to do something else with somebody else.
"We made some real mistakes and defended poorly at times. It was a real scrappy affair with some rubbish defending and rubbish attacking which could have finished 6-6!
"We can't afford to let 14 goals in five games. Birmingham keeps nicking games and they don't give many goals away - eight this season.
"They haven't been scoring many but they've been solid. That's a promotion-winning outfit."
Wolves started conceding heavily on September 30 when they lost 3-0 at home to Reading. Things only got worse when they conceded another three at Swansea a week later. They then seemed to get things back on track with a 2-1 victory at home to Coventry, though a week later they let in five goals away at Norwich. Though they where back to winning ways against Watford but McCarthy is unhappy with the situation and has threatened changes.