The Alpha Dog star was called in to replace Shia LaBeouf following his headline-grabbing departure in February (13) and the production, about two young brothers who kidnap a wealthy businessman, opened on Thursday (18Apr13) to rave reviews.
However, Foster admits he owes his success to the Harry Potter star because he's the one who inspired him to take a chance on the project.
He tells New York Magazine, "I talked with Dan Radcliffe when we were doing Kill Your Darlings, and he had done Equus and so many plays, and I have so much respect for him - he's such a brave man - and he was like, 'Oh, you should do a play!' 'Well, I'd really like to, but it scares the s**t out of me.' So when this showed up, how do you say no? You go do something that scares you."
And the 32 year old is glad he accepted the job - because he's been having a great time with his co-stars, theatre veterans Alec Baldwin and Tom Sturridge: "I love Alec; I was just struck by how different we all are, but we have similar values. Hopefully that resonates in the play. We all have our way; we've all had our moments. But what's beneath all of it is so much care and respect and making sure the others are all right...
"(Sturridge is) really the senior here, in terms of theatrical experience - well, both of them are. I've relied on them heavily in terms of asking questions about rhythm versus impulse of emotion. By the time I got there, it was just about not sleeping and catching up to these guys."