An era never ends as cleanly as it might. What, for instance, marked the true end of the Atlanta Braves’ dynasty? It may have been last October, when the team’s longtime general manager, John Schuerholz, announced his retirement. It may have been a year before, when the team failed to win its division for the first time since 1990. It may even have been after the 2002 season, when Tom Glavine, then the longest-tenured player on the team, left for the Mets as a free agent.

As much as each of these events marked the end in their way, though, when we look back years from now, John Smoltz’s announcement, made yesterday, that he will be undergoing season-ending surgery will rank with any of them. Because he’s 41, a shoulder operation is likely to end Smoltz’s career, and with it Atlanta’s last unbroken link to the days before the dynasty, when they were built around Dale Murphy, were managed by Chuck Tanner, and lost 95 games every year. A great deal has happened since, and Smoltz is the only player who was there to see all of it.

If this is the end, Smoltz is a cinch for the Hall of Fame. The only man ever to win 200 games and save 150, owner of a spectacular postseason record (15-4 with a 2.65 ERA in 207 innings), an eight-time All-Star, two-time wins leader, a Cy Young award winner, and one of the anchors of a team that won its division every year for a full decade and a half, racking up five 100-win seasons, five pennants, and a World Series victory along the way, Smoltz is absurdly overqualified for Cooperstown. Still, it’s worth looking a bit more closely at that first, signal achievement, which, unique as it is, nonetheless may have a bit more hype than substance to it.

The basic facts are this: In 2000, Smoltz blew out his elbow and underwent an arm operation. On his return the next year, he continued to suffer arm problems, and after two long stretches on the disabled list, he finally did what he’d been wanted to do for years, moving into the Atlanta bullpen as a closer. In 31 games he ran up a 1.29 ERA, and for the next three years he terrorized the league, saving 55 games in 2002 and posting a 1.12 ERA in 2003. His years as a closer, even more than his time as the third ace in the legendary Atlanta rotation, are what have cemented his Hall of Fame case while equally strong pitchers such as David Cone, Kevin Brown, and Mike Mussina are considered borderline cases at best. Other than Dennis Eckersley, no one has really done anything like what Smoltz has done.

Whether that’s as valuable as it’s taken to be is open to debate. One lens through which to look at the problem is a statistic called leverage index, put together by researcher Tom Tango and available at fangraphs.com. Its basic premise is simple: Some game situations are more important than others, and one can measure how difficult the situations a pitcher is in and credit him for them. A starter will usually have a leverage index of 1.0, meaning that he’s pitching innings of precisely average value. A closer who comes into a lot of tight games will usually have one approaching or exceeding 2.0, meaning his innings were about twice as important as those of a starter.

The interesting thing is that this method tracks the actual value teams put on relievers pretty well. In a typical year, Mariano Rivera will pitch 80 innings with a leverage index of 2.0, meaning that in a broad sense one could say he’s about as valuable as a starter who pitches 160 innings of equal quality. That’s 70% of the 225 innings a top ace starter will pitch. Rivera, the best-paid closer in baseball, is paid about 70% of what Johan Santana is paid. This works as you go on down the line; the price of a closer tends to be a bit less than three-quarters the price of an equally good starter.

If you scale up Smoltz’s years as a closer this way, multiplying his innings totals by his leverage indexes, it’s clear that he’s probably getting a bit too much credit for them, at least if they’re taken to be anywhere near as valuable as those years when he pitched 240 innings with ERAs around 3.00. In 2002, his season was basically equivalent to that of a starter who pitched 162.1 innings with a 3.25 ERA; in 2003, he was like a starter who pitched 107.1 innings with a 1.12 ERA; in 2004, like one who pitched 151 innings with a 2.76 ERA. Those are creditable seasons, but none but the second is really spectacular or Hall-worthy. Judged on a starter’s scale, those 150 saves would probably have come out as something like 35 wins had Smoltz had seasons of exactly equivalent value in the rotation, leaving him with many fewer career wins than Mussina has now.

None of this means that Smoltz isn’t a viable Hall of Famer, or that his accomplishment in preserving his career in relief before moving back into the rotation in the late years of his career and pitching several superb years isn’t especially noteworthy. It’s staggering, actually, and no one should be surprised if he manages to add to his legend by fighting back from his latest injury and running up another strong year or two in relief before retiring for good. Still, Smoltz wasn’t great because of some freak number like 200/150; he was, and perhaps still is, great simply because that’s what he was.

tmarchman@nysun.com