Everybody knows that young hurlers are a crapshoot no matter how highly touted they are, Kerry Wood notwithstanding. It generally takes a rookie pitcher 2-3 years to establish himself in the majors. It takes a minor league teenager even longer. And there's always the threat of overuse resulting in arm trouble. Avoid closer prospects.
Most managers are leery of throwing a youngster out there in a late inning pressure situation.
If you need some save insurance, grab the relievers setting up the guys who are inconsistent or coming off an injury. Ignore defensive players . Middle infielders and catchers that rely on their glove rather than their bat do not make good reserve picks. Sometimes the reverse is true too. Many players that hit well in the minors find their playing time curtailed when they get to the bigs because their defense is below average.