The Scotland international's form has been a rare positive for the Bluebirds this season as they battle against relegation.
Solskjaer now expects Marshall to continue his form until the end of the campaign and help the team secure their top-flight status.
"He has been terrific this season and he is a vital part of my squad," the Norwegian told the club's official website. "He's going to be immense and phenomenal over the next seven games, I'm sure of that. He's been absolutely top.
"I've said he's in the top three or four goalkeepers in the Premier League."
Marshall recently signed a contract extension with Cardiff until summer 2018.