Baseball fans mourned the death of all-time great Willie Mays while gearing up for the great debate brought on by his passing: who is the greatest living ballplayer?

The title, GLB for short, is baseball shorthand for the most accomplished, retired position player or pitcher who hasn't yet been promoted to the big dugout in the sky. While it is a completely subjective title, Mays had enjoyed a loose consensus as the holder of the GLB moniker.

Before Tuesday, Mays was "baseball's greatest living player, no dispute about that,” longtime baseball commentator Bob Costas told Bay Area radio station KGMZ on Wednesday.

If there was any challenger to Mays as the greatest living ballplayer in recent years, it would have been one-time home run king Hank Aaron, who died three years ago.

Asked who the greatest living ballplayer is, de facto MLB historian Ken Burns refused to have that conversation without "Hammerin' Hank" or the "Say Hey Kid."

"Without Aaron or Mays, no comment," said Burns, best known for his "Baseball" documentary.

The invention of the GLB title is largely attributed to New York Yankees legend Joe DiMaggio, who insisted on being introduced as the “Greatest Living Ballplayer” at events until he died in 1999.

Even if DiMaggio really wasn't the greatest living ballplayer, the title stuck and took on a life of its own.

The purely subjective title now has a modern objective measure, known as "wins above replacement" (WAR), which attempts to gauge a player's value over his potential replacement. This tool could be valuable in settling the GLB debate, if not for the steroid era that called all numbers of the early 2000s into question.

Mays is No. 5 all-time in WAR with 156.2 wins above replacement, according to Baseball Reference, and nominees to take his GLB title could include:

- Mays' godson and fellow San Francisco Giants icon Barry Bonds, who had a 162.8 WAR and hit an MLB-record 762 home runs. However, he's now best known for his association with the performance-enhancing drug era of MLB, and baseball writers have kept the 59-year-old out of the Hall of Fame despite his remarkable numbers.

- Roger Clemens, 61, was the most dominating pitcher of the late 1980s and 1990s. He has a 139.2 WAR but suffers the same fate as Bonds as a PED-era player.

- Fellow PED-tainted great Alex Rodriguez, 48, was a near-teenage sensation and seemed like a Cooperstown shoo-in as a youngster before he too was linked to drugs. He is No. 16 on the WAR list at 117.6.

- All-time stolen base king Rickey Henderson, 65, has the greatest WAR figure, No. 19 at 111.1, of any living former player who has no ties to the steroid era. Henderson made it to Cooperstown in 2009.

- Starting pitcher Greg Maddux, whose pinpoint control made him a 355-game winner over 23 MLB seasons, has the greatest WAR of any living hurler at 106.6, No. 28 all-time. The 58-year-old was enshrined into the Hall of Fame in 2014.

- Brooklyn-born lefty Sandy Koufax, 88, was the hands-down most dominant pitcher of the early 1960s. But chronic elbow injuries kept his brilliant career relatively short. The 1972 Hall of Fame member has a WAR of 48.9, No. 333 on the list, just behind active slugger Bryce Harper.

- Ken Griffey Jr.'s career included the PED era but he was never tied to the scandal as he hit 630 home runs (seventh most in MLB history). The 54-year-old's WAR of 83.8 is No. 58.

- Pete Rose, 83, has more base hits (4,256) than anyone but has been kept from Cooperstown due to his ties to baseball betting. His WAR is 79.5, good for No. 67, just behind active pitcher Clayton Kershaw.

"Clearly, this question about 'Greatest Living Ballplayer' is between those who include Barry Bonds and those who refuse to," Boston Globe columnist Bob Ryan wrote shortly after Mays died.

The GLB debate is so thorny that MLB Historian John Thorn politely sidestepped the question.

"I believe that as MLB’s official historian I am obliged to consider facts rather than offer an opinion about an opinion, so I must pass on this question," he said in a statement to NBC News on Thursday.

And Roy Johnson, a columnist for the Alabama Media Group, suggested that the GLB title needs to be retired with Mays' passing.

"Let it go. Let the phrase go. I’ll never use it again. None of us should," Johnson wrote on Wednesday. "It’s a lazy phrase, anyway. An easy out. An easy way to dodge the debate. To duck the declaration. To dismiss the definitive."

As fans and analysts weigh in on the debate, the discussion about the greatest living ballplayer not only honors Mays' legacy but also brings to light the remarkable careers and achievements of other baseball legends. Whether the title continues to be used or is retired, the debate underscores the passion and reverence baseball fans have for the game's history and its iconic players.