"We need to get him back and fit to play for Portsmouth in the next two weeks. That's the key.
"We spoke to the doctors and they know he's not fit. I think he will report and then come back to us."
And with Steven Gerrard and Owen Hargreaves rated doubtful, McClaren could ill afford to loose an experienced campaigner like Campbell.
Redknapp continued: "We've got to treat Sol and try and get him fit for Liverpool. He is a very important player for us.
"He had a groin problem and now he's gone to his hamstring. He definitely won't be fit to play for England. It is a shame, for sure."