Only three career-long closing pitchers have been inducted in the Baseball Hall of Fame: Rollie Fingers, Rich Gossage, and Bruce Sutter.

Three other Hall of Fame relievers -- John Smoltz, Dennis Eckersley, and Hoyt Wilhelm -- spent large chunks of their career as starters.

Point being, it ain't easy to be a fireman.

Save for one notable exception, we haven't seen any Gossages or Sutters over the last couple of decades, but there have been plenty of terrific closers. Who was the best? We'll use FanGraphs' numbers to answer that question.

Fangraphs' wins above replacement (WAR) is the overall measure by which we selected and ranked the top 15 relievers of recent years. WAR, for the uninitiated, t's a popular baseball metric which summarizes a player's total contributions to their team. It acts as an estimate in answering questions about how much value a team would lose with so-and-so out.

WAR is calculated for position players and pitchers alike, but for pitchers, there are many things that make up the hallmark statistic. For all of these factors, or to simply read more on WAR, you can visit the FanGraphs library.

You will also see other metrics listed along with each pitcher. This sabermetrics snapshot includes runs allowed based-WAR (RA9-WAR), runs above replacement (RAR) as well as batting average on balls in play wins (BABIP wins), fielding dependent wins (FDP-Wins) and left on-base wins (LOB-wins), all of which assign a replacement-level win number based on different formulas.

This will provide us an in-depth look at why these hurlers are the top relievers over the past 15 MLB seasons. So, without further delay, here they are!