The 31-year-old West Brom stopper was due to link up with the rest of the Wales squad for Saturday's friendly in Cardiff.
However, Myhill will instead stay with the Baggies to have treatment on an Achilles problem and ligament damage to his left thumb.
Myhill has been struggling with the niggling injuries which last week prevented him from training until the eve of the Chelsea game.
"I am going to need treatment on a couple of injuries I've picked up in recent weeks and need to get over," Myhill said on Albion's website.
"I've not trained for a while and I'm glad for the rest because it means I can do some work in the gym with the physios.
"So, the break has come at a good time for me," added Myhill. "I was really struggling last week and I'm grateful to the medical staff for the help they've given me to get on the pitch."
Manager Chris Coleman has not yet decided whether to call up a replacement with the rest of the squad due to report for duty on Wednesday.