The Tampa Bay Rays' record of drafting in Andrew Friedman's time as their general manager was spotty, including the moment when they passed on Buster Posey and chose infielder Tim Beckham. There also were mistakes on free agents such as Pat Burrell.
But Friedman's era in Tampa Bay was an overwhelming success, which is why the Dodgers stalked him with promises of potential and power until he agreed to take over their baseball operations. What the Rays probably did better than anything was build bullpens, year after year, despite constant turnover because of the team's financial limitations.
Consider the composition and work of the Rays' bullpens from 2008-14.