Maggie Gyllenhaal will replace Toni Collette in Sam Mendes’ untitled relationship comedy for Focus Features.Film, which stars John Krasinski and Maya Rudolph, is about a young couple who travel around the U.S. searching for a place to put down roots. Dave Eggers and wife Vendela Vida penned the original screenplay. Gyllenhaal will play a bohemian college professor who is an old friend of the character played by Krasinski. Collette dropped out of the film due to scheduling delays on the shoot, which recently got under way in Connecticut. Gyllenhaal begins lensing her role next week. Gyllenhaal next appears in Warner Bros. summer tentpole “The Dark Knight” as Rachel Dawes, Batman’s love interest. She is repped by CAA, Benderspink and attorney Alan Hergott.