In announcing the moves, Coach Dave Wannstedt said Collier was reassigned because of health-related issues.
"From a personal and organizational standpoint, everybody knows we totally support Joel and we'll help him get through this and further his career," Wannstedt said. "Everybody knows what he means to our organization, and he'll continue to be a major influence in what we do."
Both Wannstedt and Collier declined to discuss specifics of Collier's health issue. It was the reason Collier missed all three days of the quarterback school last week.
"The health issue equated to a level of exhaustion," Collier said. "Post-minicamp, I felt it was in the best interests of the everybody to taper me down.
"It could be day-to-day or week-to-week, we just don't know. That's why I wanted to take a step back."
As for Foerster, he was hired this offseason after spending two years as the tight ends coach for the Indianapolis Colts.
Prior to that, he spent six seasons with the Tampa Bay Bucs and three with the Minnesota Vikings.
"The circumstances of how this came about were unfortunate, but I've thought about and prepared for this for a long time," Foerster said.
"Myself compared to Joel have different personalities, but the things we are trying to accomplish are exactly the same."