I hate to say it, but with how random relievers are other than a small group of elite closers, I think Rizzo has had it right for the past decade. Bring in a bunch of wildcards in the offseason, see who sticks, and if the team is in contention at the deadline bring in more arms.
I think it works more often that not, and seems the Nats giving a guy a multi-year contract is amount to killing that guy's career.