It is real and he is also the one posting to it. (So we should be spared the weird third person Tweets on the @BusterPosey Twitter account) I just checked and he has 11,056 followers. That was fast.
The article also has a list of other players with Twitter accounts… and I don’t think there is any doubt that Crawford, Romo, Affeldt, etc are doing their own Tweets.
I know fans expressed concerns about Vogelsong’s flu being contagious. Apparently it is actually back issues that are contagious.