Robertson is part of Scotland's squad this week.
Snodgrass said: "There's only so much you can do but he's dealt with everything Steve Bruce has thrown at him - some big tests. You always hear about whether someone can cut it at the top. Well the only way to find out is to give them a chance. The manager has done that so fair play to him and fair play to Robbo for taking it.
"When Andy did come down, the first thing I told him was to believe that he could cut it there. You go in there with no fear like he did, and show people what you can do. He's got a great left foot and the way he attacks is terrific. He's learning each day and that's good. He's in the gym working hard on his upper body and physique."
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