At the 2011 trade deadline, the Texas Rangers sent two of their best prospects -- Robbie Erlin and Joe Wieland -- to the San Diego Padres for Mike Adams, who had been a dominant reliever to that point -- a 1.13 ERA in 48 innings -- and was under contract for the following season. Adams continued to pitch brilliantly down the stretch and was the Rangers' third-most valuable pitcher in the playoffs according to WPA.
Thereafter, Adams' star faded rapidly. He pitched well but not spectacularly for the Rangers last year and was an average reliever for the Phillies this year before being diagnosed with a torn labrum.
Adams' rapid fall from grace is not atypical for a relief pitcher. Dave Cameron recently compared stud relievers to perishable food, and Bill Petti demonstrated that relief pitchers generally age less gracefully than starters.
This, in turn, makes relief pitchers the perfect deadline acquisitions -- capable of playing an outsized role in the playoffs, where top relievers throw a larger fraction of the innings, while simultaneously unlikely to be a significant part of the next winning team for a rebuilding franchise.
We've already seen Francisco Rodriguez get traded in the past few days, and you can bank on a few other relievers moving between now and 4 p.m. ET Wednesday.
With the help of the Steamer projection system, I've identified the three most and least desirable relievers on the market in terms of expected cost compared to projected performance. Some of these guys are far more "available" than others, but relievers tend be the kind of players that get moved the most this time of year. (The projections shown are park, league and defense neutral to put pitchers on a level playing field.)