The Seattle Seahawks have placed 4 players on the active/Physically Unable To Perform (PUP) list: DE Chris Clemons, WR, Percy Harvin, TE Zach Miller, and RB Robert Turbin.
This has been reported by a number of media outlets, but I believe the first was Adam Schefter:
This is not the PUP list that requires that players miss the first 8 games on the season, like we saw with CB Walter Thurmond a year ago. That designation doesn’t happen until the end of training camp, when teams cut their rosters down to 53.
This version of the PUP is no big deal at all. The Seahawks can remove any of these 4 players from that list at any time once the player is ready to begin practicing. The team also doesn’t gain the use of a roster spot for placing players on this list, so there isn’t much meaning in the designation.
The only significance here is that only players who are still on this particular list are able for the reserve/PUP list. So that means that if any of these 4 players have some sort of setback, or their injury is more severe that currently though, then the in-season PUP list becomes an option when the team is trying to make cuts and get down to 53 players.
It is not uncommon at all for players to only spend a couple days on this PUP list.