The 'Sherlock Holmes' star said it is a delight to watch her performing on the sets of the film, which is an adaptation of the Pulitzer and Tony-winning play of the same name, reported OK! magazine.
"Meryl was extraordinary. The hardest thing with her is to actually act. You just want to sit and watch her. You want to be in the audience," he said.
The film, which is directed by John Wells, revolves around the women of a family whose lives have splintered in many directions until a crisis bring them back to their childhood home.