The Will & Grace actress signed up to star in the Terrence McNally comedy, about two married couples spending America's 4th of July holiday weekend together at a beach house in the Hamptons.
Previews were due to kick off on 9 April (10), with the show officially opening later in the month (Apr10) - but Mullally's sudden departure has thrown rehearsals into chaos. The show's debut has been delayed, but producers are hoping opening night on 29 April (10) will go ahead as planned.
Mullally's departure is rumoured to be linked to her frosty working relationship with the play's director Joe Mantello.
Todd Haimes, artistic director of the Roundabout Theatre Company, released a statement on Wednesday (24Mar10) confirming the actress' sudden exit.
It reads, "We were surprised and disappointed that Megan Mullally had to withdraw from the production immediately in breach of her contract. With the loss of Megan in a four-person ensemble, work has been delayed after only two weeks of rehearsal. We have wanted Joe Mantello to direct this comedy since he staged a reading for us three years ago. We expect to announce replacement casting shortly."
It is not yet known whether producers will file a grievance with the Actors’ Equity union over Mullally's alleged breach of contract.