I suffered through the loss of a starting quarterback to retirement. It destroys a fantasy team. It hampers a NFL team's offense. It won't have as great of an impact as it would have had a few years ago. Each team has the chance to make quick moves through free agency.
Most teams have other vital parts in place to remain intact.
The Broncos are a prime example. A top-flight running back, a hall of fame tight end, and an above average line will keep their horses running into the next century. Most fantasy owners spend a high pick on the great QB's. Usually a good move, unless the QB is Elway. In my league a Elway led and Bronco dominated offense fantasy team lost the Championship due to the poor performance of Elway.