He said: "It's been an issue for four to five years. We need to address it.
"We've got players who do fantastic in European club competitions but in internationals we don't click.
"It's something we've looked at."
The Chelsea defender roared a warning for England's World Cup qualifiers.
He said: "We really have to step up and be counted. We're a great side. Everyone wants to beat us. Hopefully our quality will come through."