'Moneyball' director Bennett Miller was unsure if the movie would ever be completed.
The new film stars Brad Pitt as former Major League player and Oakland Athletics manager Billy Beane but Bennett – who replaced Steven Soderbergh as director - admitted even with the Oscar nominee on board he worried about ever finishing the film because it is so "complex".
He told Sports Illustrated magazine: "It seemed like a shoot-the-moon project because it was complex and messed up in a thousand different ways.”
Although he has impressed with his portrayal of Beane, Pitt admitted he wasn't a fan of baseball before starring in the movie.
He said: "My relationship with baseball was cantankerous at best. I had a crap arm. I couldn't hit. My career ended with 18 stitches under my eye after a pop fly at high noon. It was not my gift."
Brad also refused to watch past baseball films including Kevin Costner's 'Field of Dreams' and Robert Redford's 'The Natural' because he thought this project had themes which "went beyond the playing field".
He added: "I thought this was a contemporary story, and I thought there were bigger, universal themes that went far beyond the playing field that I was most interested in. In some ways, the film still holds the romance of the sport. On the other hand, it's anti-conventionality."