Childress told KFAN radio in Minneapolis: "I don't know if he's going to play next year, and I don't know if he knows if he's going to play next year."
Childress said he wants Favre to make the best decision for himself.
The coach also believes Favre's surgically repaired ankle will not factor into the 40-year-old's decision. Childress said Favre is running stadium steps in a weighted jacket to slim down.
Many expect Favre to return for a 20th NFL season, but Childress said he wouldn't be surprised either way.
Favre said Tuesday that he and Childress didn't discuss a timetable for the quarterback to decide on a return, and he wasn't given a deadline, either, according to USA Today.
"If I could guarantee it, I would, Favre said. "Obviously, I can't make people understand what I'm going through."