Baseball's ninth inning is often unlike any other frame in the game. Win or go home. Now or never. Do or die.
Given the ninth inning's magnitude, managers have long asked their top relief arms to tally the final three outs of close wins.
So who are the best all time under the ninth-inning spotlight? Many can agree on two names: the Yankees' Mariano Rivera and Trevor Hoffman, primarily of the Padres. A pair of likely future Hall of Famers -- first and second, respectively, on baseball's all-time saves leaderboard -- Rivera and Hoffman combined for 20 All-Star Games and countless other accolades.
In fact, they were so good for so long, that MLB named awards after them.
The Trevor Hoffman Award for the National League's top reliever was first handed out in 2014, with then-Atlanta closer Craig Kimbrel taking home the honors. Two years later, Kimbrel is now set to join the American League -- following an offseason trade from the Padres to the Red Sox. This year, then, will mark his first chance at the Mariano Rivera Award for the AL's top relief arm.
Kimbrel, who made his Boston Spring Training debut on Friday, is entering his seventh season, which is far fewer than Rivera's 19 or Hoffman's 18. But perhaps we've reached the point at which Kimbrel's name can be compared favorably to any relief arm in history.
Want evidence? Let's compare Kimbrel's five full big league campaigns (2011-15) against the superlative half-decade runs enjoyed by Rivera and Hoffman.
Although Kimbrel debuted on May 7, 2010, he did not pitch his first uninterrupted big league campaign until the following year. He's been an unstoppable force in the five seasons since, notching 224 saves with a 1.70 ERA, a 0.91 WHIP and 14.4 strikeouts per nine.
Identifying Rivera's best five-year span is no easy task, given the indomitable reliever's prolonged run at greatness. But for the sake of argument, let's look at the Yankees legend's 2005-09 efforts, when he recorded three of his four lowest ERAs, two of his three best WHIPs, three of his five top WAR totals and his best K/BB ratio. Amid this excellence, Mo had a pair of top-5 AL Cy Young Award finishes, including a runner-up designation in '05.

Now that we have identified Rivera's most remarkable span, let's take a look at the apex of Hoffman's extended peak. The San Diego legend's best half-decade is easier to identify -- 1996-2000 ,to be exact. Hoffman finished seven seasons with a sub-1.00 WHIP, with four of them coming in this span. Additionally, four of his six highest K/9 rates fell during this stretch, as did three of his six best ERA+ campaigns.
So now that we have picked out five-year chunks of greatness for each of the three relievers in this study, let's run a comparison across 12 statistical categories, awarding a gold, silver and bronze for each one.
(Note some stat definitions: ERA+; aLI referes Average Leverage Index (where the higher the number, the higher leverage the situation); OPS+ against; IRA% refers to Inherited Runs Allowed Percentage; and WAR refers to wins above replacement.)

Summarizing the 12 categories up for consideration, Kimbrel takes home six golds, five silvers and one bronze. Rivera claims five golds, two silvers and five bronzes, and Hoffman holds a single gold, five silvers and six bronzes.
Through this very specific lens of peak work, Kimbrel stands shoulder to shoulder with two of the most decorated, respected and successful closers the game has ever produced.
The breadth and height of Kimbrel's career-opening dominances occupies rare territory, one where searches for superlatives demand a thesaurus. However, Rivera and Hoffman redefined relief greatness for nearly two decades each.
For Kimbrel to match their level of reverence among the game's elites, he will have to extend his magnificent work over the remainder of this decade, and that will be the tough part, considering he just posted a career low ERA+ in 2015. Regardless, we should appreciate that we're watching one of the game's all-time great closers.