Vikings coach Mike Zimmer said Peterson was excused from Wednesday's practice because of an undefined personal matter. Greenway is dealing with what Zimmer called "a little bit of a wrist" problem.
Peterson isn't expected to play in Minnesota's third preseason game at Kansas City on Saturday night anyway.
Eyebrows raised when word spread that Greenway had a wrist injury. The linebacker finished last season with a fractured right wrist.
"He's been MRIed and X-rayed, I just don't want to irritate it more," said Zimmer. "It's not broke, I know that."
The Star Tribune notes that Greenway sprained his right wrist during Week 7 last season and fractured it in two spots the next week, but he did not miss a game because of it.
According to The Viking Age, the team had hoped an offseason of rest would allow Greenway's wrist problem to recover, but it's apparent that a solution isn't that simple. It could be something that hangs with Greenway for awhile, maybe even the rest of his career, Viking Age notes.
Greenway will be the Vikings' starter at Will linebacker for the season opener in St. Louis. He has led the team in tackles each of the past six seasons, so the team will do what it can to try and keep him healthy.