Ask the Rams how important special teams are.
And then ask yourself, can you replace Ken Walker, and maybe go RB by committee and have success?
Can you replace Shaheed and have the same special teams impact with another returner?
I think you are likely to go RB by committee anyways and have success than attempting to replace a game changer in Shaheed and having the same success with a cheaper alternative.
Shaheed is also a team player with incredible football IQ. I love K9 but I think Shaheed makes so much of a difference that you can replace K9 with young RB and you may not replace Shaheed that easily.
Seattle was not great on special teams until Shaheed was on the team.
Special teams for Seattle changed the landscape of the team completely when Shaheed became the returner.
When Seattle traded for Shaheed, Seattle, became legit champion contenders because the special teams became elite.