The pair face eachother tonight as Robertson's Scotland meet Bradley and Northern Ireland in an all British friendly.
Robertson told Sky Sports: "The performance at home against Chelsea is one of the best I have seen from a full-back.
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"There were probably not many who knew him beforehand, but it was a special performance.
"That was also why I subsequently told him that he has to perform regularly now.
"He has shown that he has the skills. He has shown, he has the attitude. He has everything you need to become a top, top back, but now he just has to do it week in and week out."