The Oscar winner originally took on the role of Jack, a romantically-challenged chauffeur, in the 2007 Off Broadway production of Bob Glaudini's play, but he wanted to cast a new star when he decided to turn the stage show into a movie.
Hoffman refuses to identify the mystery man he had in mind to step into Jack's shoes, simply saying, "We found someone pretty wonderful that would have been pretty amazing and he wanted to do it."
However, Hoffman found himself reprising the character when the cameras began rolling on his film version because his leading man was unavailable to shoot during the winter.
The actor-turned-director admits he struggled to do double duty on the set of the movie and found it difficult to get into the right frame of mind to portray Jack.
He explains, "(Acting) is a different beast. You've got to create a sense of privacy. You have to create a sense of focus that's so sharp and so specific that you have to hold over for a period of time."
Hoffman even had to walk away from the shoot several times during one intense scene with his character's love interest, Connie: "That day was a really hard day... I did a lot of takes.
"There were moments like that where it got kinda dark. That's when I had to grow up and I'd leave the set, get by myself and go, 'You're not a director, you're an actor', and do what I need to do, go back and do it."
And his experiences on Jack Goes Boating have put him off working as director and actor in any future projects - he adds, "I don't want to direct myself again."