Jonathan Papelbon is the 27th member of the 300 Saves Club. (Matt Slocum/AP)

Phillies closer Jonathan Papelbon notched his 300th career save Tuesday night, a significant number given that the five relievers in the Hall of Fame have an average of 314 saves and that only two active pitchers, Joe Nathan and Francisco Rodriguez, have more. At the same time, 300 saves is just 46 percent of Mariano Rivera's record total of 652 and merely puts Papelbon in a three-way tie for 24th place on the all-time list behind the likes of Todd Jones, Jose Mesa and Francisco Cordero.

Much like pitching wins, saves do a better job of marking time than they do measuring performance. Whereas wins are heavily dependent on run and bullpen support, saves rely in large measure on opportunity (a situation must meet certain criteria for a save chance to be on the line), and in both cases, a pitcher can perform poorly and still add to his total. Wins and saves leaderboards tell us very little about who the best starting and relief pitchers were in any one particular season, but over the span of careers, totals in those categories can at the very least direct us toward pitchers whose work deserves further examination.

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Papelbon's 300th save reminded us that, despite his declining velocity (down three miles per hour from 2011) and strikeout rate (also down for the third straight year and now below league average), he is now in his ninth season as a reliable and often dominant closer. Over that span, he has converted 88 percent of his save attempts and posted a 187 ERA+, both marks he has exceeded thus far this season despite his declining peripherals.

But even as Papelbon reaches what should be a milestone mark, saves have never really acquired a magic number on par with 300 wins, 500 home runs or 3,000 hits. In fact, 300 once looked like it was going to be that milestone, as four of the five relievers now in the Hall of Fame reached that plateau: Bruce Sutter (300), Goose Gossage (310), Rollie Fingers (341) and Dennis Eckersley (390). Looking at the career leaders, however, 400 would seem a far more appropriate place to put that milestone.

The following chart shows how 400 saves measure up to Rivera's all-time record, as well as the commonly accepted milestones in wins, home runs and hits for the respective career records in those categories. Working off the fact that 300 saves is just 46 percent of the record, it also shows what 46 percent is of the records in those categories and the percentage that the milestone figure is of the all-time record.

SV W HR H Record 652 511 762 4,256 Milestone 400 300 500 3,000 MS% 61% 59% 66% 70% 46% 300 235 351 1,958

What we see here is that 300 saves are on par with 235 wins, 350 home runs or 2,000 hits, all impressive totals, but not the kind of major milestones that prompt Hall of Fame conversations. However, 400 saves aren't out of place with the accepted milestones in those categories, lining up almost perfectly with 300 wins as far as being a percentage of a record set by an extreme outlier (Rivera, who had 51 more saves than second-place Trevor Hoffman; and Cy Young, who is 94 wins ahead of second-place Walter Johnson).

Thus far, only five men have saved 400 games. That's enough to prove that the milestone is reachable, but exclusive enough to still make it meaningful. Of those five, Rivera and Hoffman (601) appear destined for the Hall of Fame. Lee Smith (478 and the record holder for 13 years before Hoffman passed him) has fallen short of induction for 12 years, though he was named on more than half of the Hall of Fame ballots in 2012. John Franco (424) received just 4.6 percent of the vote in his only year on the ballot, and Billy Wagner (422) seems likely to fall short as well after becoming eligible in 2016.

Given his struggles this season and the fact that he'll be 40 in November, active leader Joe Nathan (354) is no lock to become the sixth man with 400 saves. Papelbon, who will turn 34 in November, is not a lock for that milestone either, despite a vesting option in his contract that could make him a $13-million player through 2016. The next two active leaders are real longshots. Jose Valverde (288) appears to be finished adding to his career total and 30-year-old Huston Street (252) isn't anywhere close to 300.

The most compelling active pitchers in terms of career saves remain the Brewers' Francisco Rodriguez, who at 32 is more than a year younger than Papelbon and 23 saves ahead of him on the all-time list, and the Braves' Craig Kimbrel, who has 157 career saves and is still just 26. With 19 saves already this season, K-Rod needs just six more to post his highest season total since 2009. Having reduced his walks while maintaining his strikeouts, Rodriguez is pitching about as well as he ever has and could reach 400 saves by his age-35 season, provided he can use this season as a springboard to a closing job as a free agent this winter.

Kimbrel, meanwhile, is nothing short of the best closer in baseball, and already way ahead of where some of the big names he's chasing were at his age. Rivera (five saves after his age-26 season), Hoffman (30) and Papelbon (35) were just getting started as closers at this point in their careers.

Of course, there's no guarantee that Kimbrel will have the career endurance that so many of his closing brethren have lacked. Only four men -- Rivera, Hoffman, Smith and Wagner -- have saved 20 or more games in at least 12 different seasons. With Rodriguez's next save he will join Papelbon and Nathan as having done so eight times. Kimbrel, as dominant as he has been, is on pace for just his fourth such season.

longevity, reliability and consistency

reached the total