Such has been the form of Martin Kelly that Johnson found himself moved to the opposite flank to cover the Reds weakness on the left.
His first appearance there was in the 2-1 defeat at Blackpool but he has played on the left in the five matches since, with the last four bringing successive wins and clean sheets.
"You don't become an international regular for England if you are not a good player," said Clarke.
"I worked with Glen at Chelsea and he is always a pleasure to work with.
"I think he has been re-energised with the change and he has switched to the left and proved he can play just as well there as he can on the right.
"It's always good to have adaptable players and when you have people like that who do well for you every week no matter what position they are in then it's a great position for the manager and the coaching staff."