Advocaat tight-lipped on Johnson inclusion
Johnson has not played since he was arrested and later bailed on suspicion of sexual activity with a 15-year-old girl at the start of this month.
Durham police extended Johnson's bail until April 23 on Tuesday and, after liaising with the Professional Footballers' Association and Johnson's representatives, Sunderland agreed that the winger would be allowed to resume training.
"What I always do, I pick the squad after the final session," Advocaat said ahead of his first game at the helm.
"Every player who trains has an opportunity to start versus West Ham.
"We still have some injuries, we don't know exactly who will join us."
Advocaat was appointed earlier this week after former incumbent Gus Poyet departed in the wake of the 4-0 home thrashing at the hands of Aston Villa.
That defeat left Sunderland just a point and a place above the relegation zone, but the experienced Advocaat says he is relishing the task ahead.
"I'm looking forward to the challenge, this is a great football club," he said.
"'I'm a coach that likes to control games. I have seen Sunderland have not done a lot of that. It needs to change.
"The fans need to know something is changing. We need them behind us, they can be our 12th man. We must show them what it means to us."