The Cobblers have picked up just one win and two draws from their nine league games so far this season.
"It's not good enough, simple as that. We've got well-paid professionals with a lot of experience. There's no pressure on Aidy Boothroyd. He's going to get the time to turn it around and I'm 100% behind him," Cardoza told BBC Radio Northampton.
"If we have to, we will [make signings], but at some stage you have to say enough is enough and we have to try get the best out of what we've got.
"I don't want to put too much pressure on the strikers, but we've got Clive Platt and Roy O'Donovan and they're paid a lot of money to score goals and set goals up. I expect to see that improve in the short and long term."
Northampton lost last season's playoff final to Bradford City.