According to one of the main Oilers blogs online, OilersNation, Sam Gagner is out day-to-day with an undisclosed injury, likely upper-body, after twisting away from a hit in the game against the Thrashers on Sunday. Again, there is no real elaboration on the injury, so this is about all I can tell you. Not even too sure how much time he'll miss in total.
Gagner is an 11th round pick of Peter's in the Draft pool and has averaged about half a point per game for him to start the season. He certainly shouldn't be one of the guys on the bubble for Peter's last drop in the Waiver Draft this week, since he does have some players worse off than Gagner, but this surely doesn't help.
Gagner also occupies the Oilers spot in Box 4 on the Sheet, where he was taken three times. It's too late to make any moves for Week Eight, so sit tight and hope that he's back before the weekend.