How do you judge if a closer is MLB HOF worthy?

As more relievers become eligible for the Baseball Hall of Fame, a basic question arises: How do you judge a reliever?

That’s especially important for those of us who, like me, think relievers have been overrated by many others.

I also have a personal sidebar note. I was at Busch Stadium when Lee Smith broke the then single-season National League saves record. It was the year that some games had to be moved out of Montreal’s Olympic Stadium, so I and friends got primo seats less than 30 rows from the Cardinals’ bullpen, to boot.

The recently-announced retirement of all-time saves leader Trevor Hoffman brings the question to the fore

Is he a Hall of Famer? Besides the saves numbers?

Well, he's got an ERA+ of 141, and, even more impressive, a WHIP of just 1.058. For starters, my minimum cutoffs are ERA+ of at least 110 and WHIP of 1.25 or less.

But, given that the modern closer is a one-inning person hugely unlikely to face the same person twice in a game, should we tighten these numbers?

Say, 115 on the ERA+ and 1.22 on WHIP? (That said, Smith doesn't meet my current cutoff for pitchers in general on WHIP, one reason I don't consider him a HOFer.)

Save percentage might be an additional point to consider.

Now, sabermetrics has shown us that for starters, wins have been overrated in the past.

But, given that a closer comes in when the game is ahead, and usually faces nobody more than once, this is a different situation. Compared to a starting pitcher, for a closer, the game is more “his” from the get-go.

So, I’m going to consider it a legitimate ranking tool. In Baseball-Reference, blown-saves and save percentage are available under Reliever Stats after one clicks the “More Stats” on the first line of a pitcher’s stats.

That said, we have an 89 percent save percentage for Hoffman vs. 82 percent for Smith. (Dennis Eckersley is at 85 percent, John Smoltz at 91 percent in his short relief stint, and Mariano Rivera also at 91 percent, but with far better ERA+ and WHIP than even Hoffman.)

Anyway, what other criteria would you use to judge closers? More emphasis on K/BB than starters? K/9 innings?

That said, I think that given today's specialized closers, we can't go too much below Hoffman on HOF-level standards for today. So, besides him and Rivera, one other pitcher may qualify, and that's Billy Wagner. His save percentage is only 86 percent, but his ERA+ and WHIP are closer to Rivera than to Hoffman. Being a lefty, that's even more notable.

So, there’s my sample idea on ranking modern closers as HOF-worthy.
1. ERA+ of 115 or better.
2. WHIP of 1.22 or lower.
3. Save percentage of 85 percent or better.
4. I’d tentatively suggest K/BB of 3.0 or better, but that’s very minimal.

One thing I think does NOT matter is winning percentage. B-R has a poll on that. And, per a commenter there, Win Probability Added may be another good marker. Per that commenter, a WPA of 30 or higher is a definite benchmark.

Besides Hoffman, Rivera and Wagner, who else might make the cut?