The Hornets captain missed their opener against Liverpool last Saturday following groin surgery, but he is now back in training and in contention for a return.
Asked whether Deeney was training with the rest of his teammates, Silva told Sky Sports News: "He has started normal training with the team since Tuesday.
"He is starting to come fit, he had one week of pre-season until last week and it is important now we get him fit again so he can show me his football and show everyone what he can do to help the team."
Switching to Gray, Silva added: "Of course now he has worked more time with the team. He knows better what are our ideas and what we need and now is the moment I will take the decision I believe is the best for the match."