The 35-year-old actress won critical acclaim when she recreated Julie Andrews' iconic role in the Disney musical movie, but her stunning performance was ignored by the Academy of Motion Picture Arts and Sciences and the British Academy of Film and Television.
She was nominated at the Golden Globes and the Critics' Choice Awards for her turn as the magical nanny in "Mary Poppins Returns", but lost out to Olivia Colman and Glenn Close and Lady GaGa respectively.
Blunt was also nominated for her star turn in husband John Krasinski's horror movie "A Quiet Place" at the Screen Actors Guild Awards last month (January 2019), where she scooped the Best Supporting Actress honour.
Ahead of the BAFTAs on Sunday, February 10, Marshall has lashed out at the snub.
"Well, I will say that it was disappointing, there's no question, and I think people felt that. She really did the impossible by taking on this role and doing such extraordinary work with it," he shared, reports The Sun.
However, he said Blunt's performance, alongside Lin-Manuel Miranda, would stand the test of time.
"But I will say that after the soon-to-be-forgotten awards season, which will be a few weeks from now, her performance will last the test of time and it will live forever, because it's so extraordinary," Marshall gushed.
He revealed that the mother-of-two is a "very positive person", and hasn't let the lack of Oscar and BAFTA nominations bring her down.
"Emily... sees the good, sees what she did, sees how people are responding to the film and her performance, and that's what you really carry with you," he added.