2 Birds with 1 Stallone (2002)

Lou Benedetti, a world class boxer, loves people, but he can only speak without a stutter when he's inviting violent confrontation into his life. When a head injury robs Lou of his boxing license, his only hope at a future is as a fight trainer for the upcoming Golden Gloves. Unfortunately, his speech impediment is magnified under the pressure of 30 second round breaks. Lou has 2 weeks to lose his stutter and overcome a lifetime of sociopath behavior.