Welker is the best inside route runner of his generation, a safety blanket who reads defensive keys on the same wavelength as future Hall of Fame quarterbacks who have mastered the mental side of the game. Consistently beating single coverage, he's exactly where he's expected to be when Peyton Manning's internal clock strikes zero.
It's hard to place a value on that skill. No one needs to be reminded that trust is crucial to Manning's playing style. The Broncos can move Emmanuel Sanders, Andre Caldwell or even backup tight end Jacob Tamme to the slot, but they won't have the same mind meld as Manning and Welker in tight spaces such as key third downs and in the red zone.
Prior to Welker's Denver arrival, the 2012 Broncos finished second in the NFL at 30.1 points per game. That's still a touchdown less per game than Manning has averaged with Welker in the lineup.
Welker's absence isn't a death knell. Particularly against subpar defenses, Manning's aerial attack can still be lethal with Caldwell and talented second-round draft pick Cody Latimer in three-wide receiver sets.
Where Welker will be missed is in matchups with teams featuring physical defensive backs that rough up Denver's outside receivers at the line of scrimmage. It just so happens that two of those teams -- the Seahawks and Colts -- beat the Broncos last season and loom on the September portion of this year's schedule.