Johnson, who is expected to line-up at right-back in England's friendly against Denmark, had a disappointing start to the season and looked well short of form.
Such has been the form of Martin Kelly that Johnson found himself moved to the opposite flank to cover deficiencies the Reds had there.
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."
Clarke is also optimistic about the long-term prospects of Joe Cole.
"He's not joined in with the group (for training) yet but he is on his way back and hopefully before the end of the season we will get a glimpse of the real Joe Cole," added the Scot.
"If Joe can get himself fit and focused on the pitch then he will certainly be a big asset to this squad."
This week's international games have interrupted Liverpool's best run of the season but Clarke is hopeful it will not have an adverse effect on the improvements which have been made under manager Kenny Dalglish.
"It's not ideal having the international friendlies at a time when you want all of your players together, and especially when you are on a good run," he said.
"We are hoping the international break doesn't break the momentum a little bit because we have players going to different parts of the world and we hope they will come back fit and healthy."