More than once in recent years, athletic trainers and team doctors sat in a conference room at Major League Baseball’s winter meetings and tossed around a blasphemous idea.

They debated whether to let catchers who are hit in the head by foul tips, errant backswings or collisions leave the game for concussion testing, then get back in the lineup if they are deemed OK.

Baseball officials rejected the idea. Notwithstanding the radical nature of such change to substitution rules, they wanted to eliminate any pressure on players to get back on the field quickly when staying sidelined might be safer.

The discussions underscore the heightened awareness and concern over concussions in baseball, especially for catchers and umpires who are susceptible to foul tips. The trauma happens far less frequently than in contact sports such as football, but is no less scary, as the Giants and catcher Buster Posey know all too well.

Earlier this month, Posey rejoined the team after his second career stay on baseball’s seven-day concussion list. Other Giants, including first baseman Brandon Belt, second baseman Joe Panik and outfielder Mac Williamson, have lost significant time to concussions in recent years.

While the diagnosis, treatment and oversight of concussions in baseball have improved markedly this decade, the real fear for players subject to multiple concussions is how little they know about the long-term effects.

A study of 111 deceased NFL players who donated their brains for research discovered that 110 had varying levels of chronic traumatic encephalopathy, or CTE, an irreversible brain disease. Some players have committed suicide and cited their brain injuries in notes.

Because documented concussions in baseball are so rare, similar research in that sport does not exist.

“We don’t know what the threshold is for developing long-term conditions,” said Dr. Gary Green, a longtime college team physician and now MLB’s medical director.

Baseball also has a unique problem in diagnosing concussions.

In other sports that allow unlimited substitutions, a player hit in the head can be removed for sideline testing and then reinserted. Baseball does not afford that luxury. Players are checked between innings, but even the standardized field test, called SCAT5, requires a minimum of 10 minutes. If the player is due to bat or the half-inning goes quickly, there is not enough time.

As a result, baseball’s policy is to remove a player if there is any doubt.

By the numbers 116: Appearances by players on the seven-day concussion list since its 2011 inception 35: Catchers sent to the concussion list since 2011 41: Concussions reported by major-league teams from 2011-12 10: Catcher concussions reported in the majors from 2011-12 10: Minutes, at minimum, it takes to administer the SCAT5 field test on a player suspected of concussion

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Posey was administered the SCAT5 on May 5 in Cincinnati after a foul tip to the side of his mask. He passed. Players who take shots to the head are supposed to be monitored for several days. Posey played in two more games before he started to feel woozy and told the Giants medical staff. He immediately went on the seven-day concussion list.

On May 16, Giants trainers made Posey go through a rigorous exercise routine designed to get his heart racing. They made him twist and turn to test his balance, anything to reveal concussion symptoms. None emerged, so he was cleared to play the next day after doctors from the league and players association reviewed the findings.

But the system is not foolproof because concussions are not like knee or elbow injuries, which are easy to diagnose and treat. Post-concussion symptoms can come and go.

Green, the league’s medical director, was the lead author of a 2015 paper published in the Journal of American Sports Medicine that provided the first data-driven look at concussions in baseball, made possible when MLB and the players union agreed in 2010 to a standardized electronic injury reporting system now used by all 30 teams.

In 2011 and 2012, the years examined, major-league teams reported 41 concussions. There were 266 in the minors. Of the 307 combined, catchers working behind the plate accounted for 68, 10 of them in the majors.

Six were caused by foul tips, four by collisions with other players.

Green and his colleagues are conducting a more exhaustive study that, among other things, will sort information on every foul tip a catcher absorbs based on data they began harvesting last season. That might help Giants understand why Posey seems to get clocked more than other catchers.

“Is it their height?” Green said. “Where do they set up? The speed of pitches they’re catching? Some staffs’ pitchers throw with a lot more velocity. We’re looking at all those factors.”

Green said the rate of catcher concussions from foul tips has remained steady since 2011-12, while home-plate collision concussions in the majors have disappeared since a rule banning most contact was adopted in 2014.

That is a significant development.

Former Giants catcher Mike Matheny, who was forced to retire in 2006 after multiple concussions, took pride in being able to sustain hits from onrushing baserunners who wanted the knock the ball out of his glove. But he said six of those “train-wreck collisions” led to the brain trauma that ended his career and caused symptoms that lasted 18 months.

Although two foul tips to the mask triggered his final concussion, Matheny said, “Never did I have a foul ball give me anything to be semi-concerned about.”

Experts contacted by The Chronicle believe some mild concussions go unreported because athletes either do not know they sustained one or do not want to get taken out of games. But things are changing as the sports world becomes more vigilant and knowledgeable.

“Awareness now is an all-time high level,” said Dr. Geoffrey Manley, chief of neurosurgery at San Francisco General Hospital and vice chairman of neurosurgery at UCSF.

“In my experience working with professional athletes and talking to them about persistent concussions, their view of this is completely different today than five or six years ago.”

Manley is not affiliated with MLB but works as an unpaid consultant to the Oakland Raiders.

A decade ago, Manley said, “If Buster Posey has a concussion, he’s not talking about it. It’s no big deal. ‘They just rung your bell. We’ll see you tomorrow.’

“I really do believe people are much more willing to step forward and take that (trip to the injured list) for that period to make sure they’re actually better. We’re moving toward a period of hyper-vigilance.”

When Major League Baseball created a concussion protocol in 2011, a time when the issue and the NFL’s legal exposure were in the forefront, the biggest change was implementing the seven-day concussion list. At the time, the only injury list lasted 15 days. Teams and players were reluctant to use it for head injuries, figuring the athletes would not need that much time to heal.

Green said the seven-day option has led to twice as many players going on the injured list with concussions. According to MLB, the concussion list has been used 116 times, 35 for catchers, since its 2011 inception.

The 2011 agreement also requires that every player undergo an annual baseline neurological test in spring training using the computerized imPACT test that measures cognitive acuity.

Matheny said that was a critical development.

“I would have loved to have had a baseline,” he said, calling it a “light-years jump” because it finally gave the players and team doctors an idea of what “normal” should look like.

Before a ballplayer can come off the concussion list he must undergo the same test and return to his baseline reading. He also must pass a physical exam and exertion tests.

Williamson’s symptoms returned after he passed his imPACT test and physical exams.

“Anybody can pass the imPACT test,” Williamson said last week before the Giants cut him from the team Saturday for poor performance. “I can pass the imPACT test if I was drunk. I don’t think the imPACT test is a very good test.”

But he acknowledged that every case is different. Perhaps, Williamson said, players should be required to pass the physical exertion test several days in a row before being cleared.

“I think it’s a difficult issue to deal with because we want to get back onto the field as quickly as possible and they want us back on the field as quickly as possible,” he said. “I came back too quickly because I just wanted to be back out there.”

Manley considers SCAT5 and imPACT “first-generation tests” and predicted improvements in the technology and diagnostic techniques.

Posey said no protocol will work unless the players are being honest with themselves and medical professionals. Matheny concurred and said players have to drop the macho stance.

“I didn’t have enough sense to get out of my own way,” Matheny said.

Now, as he nears 50, Matheny has to worry about long-term effects that no study can predict. He said he is symptom-free but, in the back of his mind, has some fear of the unknown.

“I’m conscious of it,” Matheny said. “I don’t run around with a helmet on driving my kids around. I get that there’s been some damage done. I’m not really wired to be too concerned about things that are out of my control. In the same breath, I want to be careful.”

Henry Schulman is a San Francisco Chronicle staff writer. Email: hschulman@sfchronicle.com Twitter @hankschulman