He suffered a concussion on Sunday after getting tackled going over the middle against the Tennessee Titans. This is the second concussion for Welker this season, so the team is going to err on the side of caution. He should be considered questionable for Week 16's game.
The Broncos used Jacob Tamme in the slot quite a bit after Welker went down in Week 14, and it worked with Tamme's four catches for 47 yards. That's not a huge game, but given the fact the Broncos didn't prepare for this, it's a nice sign. Julius Thomas will still be terrific, but the two-tight end sets have been en vogue since the New England Patriots had success with it.
Fantasy impact: Tamme is worth a look as a low-end TE1, and Welker owners can consider cutting him. Of course, at this late stage of the game, his upside in Week 16 suggests fantasy owners should stick with him.