Frank is gradually introducing the former Sampdoria winger.
"I think we have done a good job, and Mikkel has also done a good job in terms of training hard and fitness work," said Frank.
"He plays with intensity in training and he looks better and better. He started for Denmark (in victory over France), where he did well. The assist was a top action. A really good touch and a perfect cross for Dolberg who scored.
"Everything is going according to plan. He has not started in the Premier League, but now he has reached a point where he can fight for a starting place. He shows me that I shouldn't have any doubts about starting him."