By Michael Hurley, CBS Boston

BOSTON (CBS) — As Craig Kimbrel came to his set on Tuesday night for a bumpy-but-scoreless ninth inning of work for the American League All-Stars, one thing stood out — and not just because it shone in gold sparkles. It was the number “6” sewn onto his left sleeve, representing his six selections to represent his league in the All-Star Game.

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For Kimbrel, that’s six All-Star appearances in seven full MLB seasons, with 2015 being the lone year when he was not among the very best pitchers in the league. That history, combined with him subtly putting together one of the greatest closer seasons ever, got me thinking — is this guy on a Hall of Fame path?

It may not be the first time that’s been considered, but there was just something about seeing that “6” on the sleeve of a reliever who just turned 29 that made the possibility seem real.

Watching Kimbrel on a regular basis, you might not look at him and immediately think “Cooperstown.” He’s largely unassuming, displaying a lot less exuberance than Koji Uehara and Jonathan Papelbon, the two most recent long-term closers in recent Red Sox history. He doesn’t say much off the field, and aside from his unique stance while looking in for the catcher’s call, he doesn’t do much on the field except get people out.

“He has the best stuff I’ve ever seen,” said flame-throwing bullpen mate Joe Kelly last month.

Of course, Kimbrel at age 29 is not even close to warrant consideration for Cooperstown. But here’s what he’s done through 448 appearances for the Braves, Padres and Red Sox:

429 IP
1.80 ERA
279 saves
714 SO
165 BB
0.911 WHIP
14.6 SO/9
4.33 SO/BB

If we allow for Kimbrel to double his career length — a reasonable thing to do — then he’ll get to 558 saves around the time of his 35th birthday. That would place him firmly in third place on the all-time list, behind Mariano Rivera (652) and Trevor Hoffman (601), while also placing him well ahead of the next man on the list (Lee Smith at 478).

That would also give Kimbrel a chance to further climb that all-time leaderboard. If he is able to pitch until he’s 40 (Hoffman pitched through age 42; Rivera, 43) then Kimbrel would need to average about 19 saves per year to pass Rivera.

That’s all a lot of ifs, but realistically, Kimbrel wouldn’t need to catch up to Rivera to have a real shot at the Hall of Fame

Here are the names of the closers (and their saves totals and all-time rank) whose faces have been gilded in Cooperstown:

Dennis Eckersley (390, 7th)
Rollie Fingers (341, 13th)
Goose Gossage (310, 23rd)
Bruce Sutter (300, T-26nd)
Hoyt Wilhelm (228, 39th)

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Hoffman fell five votes short of induction this year, so his induction is now just a matter of time. Rivera, too, is a lock.

John Smoltz is a Hall of Famer, and he was a dominant closer for a three-year stretch in the latter part of his career, but two-thirds of his MLB appearances were starts. He ranks 80th on the all-time saves list.

Here’s a look at the career numbers of those Hall of Famers (and soon-to-be Hall of Famers).

Gossage, 9 All-Star Games:
3.01 ERA, 1.232 WHIP, 2.05 SO/BB

Fingers, 7 All-Star Games:
2.90 ERA, 1.156 WHIP, 2.64 SO/BB

Eckersley, 6 All-Star Games:
3.50 ERA, 1.161 WHIP, 3.25 SO/BB

Sutter, 6 All-Star Games:
2.83 ERA, 1.140 WHIP, 2.79 SO/BB

Wilhelm, 8 All-Star Games:
2.52 ERA, 1.125 WHIP, 2.07 SO/BB

Hoffman, 7 All-Star Games:
2.87 ERA, 1.058 WHIP, 3.69 SO/BB

Rivera, 13 All-Star Games:
2.21 ERA, 1.000 WHIP, 4.10 SO/BB

And here’s Kimbrel again.

Kimbrel, 6 All-Star Games:
1.19 ERA, 0.911 WHIP, 4.33 SO/BB

(Side note: How is it possible that despite getting endless press for two decades as the best closer in the game, Rivera’s stats still make him seem underappreciated?)

Craig Kimbrel (Photo by Mike Ehrmann/Getty Images)

In that list, only Hoffman and Sutter — like Kimbrel — have zero career games started on their resumes. Eckersley made 361 starts, Wilhelm started 52, while Fingers and Gossage started 37 games apiece.

While we’re comparing the all-time greats to Kimbrel, let’s project out his 2017 numbers for the rest of the season and see what that looks like next to Eckersley’s American League MVP season in 1992:

Eckersley (1992)
80 IP, 1.91 ERA, 0.913 WHIP, 93 SO, 11 BB, 10.5 SO/9, 51 saves

Kimbrel (2017 projections)
68.2 IP, 1.19 ERA, 0.504 WHIP, 124 SO, 9 BB, 16.2 SO/9, 42 saves

Obviously, the more he pitches, the more likely it is that the ERA and WHIP will increase. Still, it’s a fun exercise to compare Kimbrel’s current work to what’s widely considered the greatest season ever by a closer.

Going back to the overall comparisons, Kimbrel fits in quite well with the Hall of Famers. As he gets older, likely deals with an injury or two, and inevitably loses some zip on his world-class fastball, his numbers will take a hit. Yet he’s in position now to be able to absorb those statistical dips without falling out of the range of the game’s best closers.

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You can email Michael Hurley or find him on Twitter @michaelFhurley.