Since the last international break, United manager Erik ten Hag has increasingly relied on Eriksen.
Discussing his pre-selection for this month's Nations League ties, Knudsen said: "It is very pleasing that Christian has come to play more. He is an incredibly skilled player who has a high international level, and he is important to us. It is pleasing for both him and us that he has hit a flow."
Knudsen also offered a status on United striker Rasmus Højlund, who has just returned from a hamstring injury.
"Rasmus is back again, and he has started to see playing time, so he is also ready to play for the national team. He must contribute with some of the things he can do with his speed, physicality and great work ethic," he added.