The 26-year-old England international was devastated to discover this week that an undisclosed medical problem could be at the root of his fitness problems.
Graeme Souness, the manager promised yesterday that the Magpies would do everything in their power to get him back into action.
But as Newcastle declined to comment on reports that the player has a liver problem, Shepherd said: "We have heard all the talk about what may and may not be wrong with Kieron Dyer, but we have to respect the player's need for confidentiality on the matter," he said.
"But what I can say is that from the moment Graeme Souness arrived at this football club last September, neither the manager nor myself have any complaints about him.
"I have to say he has been a model professional and he has lived like a monk to try to get back to full fitness.
"When he had his latest setback this week, the lad was close to tears, and he has the full support of everyone at the club. He's not in our plans for the immediate future, but have every confidence he will be back."