It's sad to see, Groves's speech is kind of messed up now too. He used to be really sharp and witty, especially during those fights with Froch, but he just seems like a shadow of himself.
I never heard anything about Evander having speech problems, but Money problems I heard. Maybe that is the one reason that's making him mute
I saw an interview of him speaking about Wilder and AJ in the past few months, and his speech was fine. In fact he speaks better now than he did when he was fighting.
Groves was drunk the other day or nervous because he was standing next to Froch. Look at his retirement interviews, he was perfectly coherent.