Campbell said: "It's going to be hard. Hopefully John can make it but if not and, whether it's Ledley (King) or Jamie, these two guys have had great seasons and have played good football.
"They can hold their own on the international stage. They are great players and it shouldn't be a problem. Jamie has played against some of the top centreforwards and had a great season.
"So I'm pretty relaxed with that and, whoever plays there, they are going to try and do their best for their country. That's all you can ask for.
"These guys want to play for England and, as long as they give their best, then I'm confident.
"Saturday (against Iceland) was the first game I've played with Jamie and you haven't got that history of playing with either of them.
"But, with international football, those kind of things happen. If you get injuries, you've got to be able to ride those kind of situations and overcome them.
"You don't want to be crying over spilt milk. These situations happen, just like in life.
"If a problem comes up, you've got to solve it. You just talk more and try harder and put more into it because you've got to compensate."