It's Fremantle's turn to deal with Covid crises after the Dockers announced five players would be entering the AFL's health and safety protocols.
Henry and Johnson are understood to be close contacts, as they live with Chapman and Young.
Assistant coaches Matthew Boyd and Josh Carr are also in the protocols.
"It seems to be on our doorstep. Hopefully, we can limit it to what we've released already," Longmuir said on 6PR on Wednesday.
A somewhat lucky run has drawn to a close, however, with coach Justin Longmuir forced to separate the playing group due to rising cases within the WAFL competition.
"A lot of our players played at Peel on the weekend, so we need to mitigate that risk," Longmuir said to the media.
"We'll probably have to do that for the foreseeable future. It's not the ideal situation for the camaraderie."
Lachie Schultz is expected to return after missing Fremantle's drubbing of Essendon due to health and safety protocols, training on Wednesday.
The Dockers have a massive clash with Carlton ahead on Saturday night.