PEORIA, Ariz. -- Nearly three years ago, Glenn Hoffman, then a coach with the Dodgers, was standing just off the infield grass near third base at Kauffman Stadium in Kansas City when he was smoked in the head by a line drive during batting practice.

"I was reading balls off the bat, and it caught me off-guard a little bit," Hoffman, now the Padres' third-base coach, said. "The cage was pushed back too far behind the plate, and I didn't expect the ball to get around the cage."

Hoffman, an older brother of San Diego closer Trevor Hoffman, sustained a concussion and missed three weeks. When he returned, for a while he wore a full batting helmet in the coach's box and then went to a protective sleeve, which he has worn ever since.

He's not the only one. Rockies first-base coach Glenallen Hill and Giants third-base coach Tim Flannery have also been wearing protective coverings. But as of the first exhibition games this week in Florida and Arizona, and into the regular season and postseason, it will no longer be voluntary.

Based on a rule adopted at the General Manager's Meetings in Orlando this past November, all Major League and Minor League base coaches must wear at least the standard batting helmet, with or without earflaps. That part of it is an individual choice.

The new rule came into being after the death of Minor League coach Mike Coolbaugh. While coaching first base for Colorado's Double-A Tulsa affiliate last July 22, Coolbaugh was hit below the ear and knocked unconscious by a line drive off the bat of Tulsa's Tino Sanchez. Coolbaugh was taken to Baptist Medical Center-North Little Rock, where he died.

A member of Team USA, which won its only baseball gold medal during the 2000 Summer Olympics in Sydney, Australia, Coolbaugh was 35 and had only become a coach for the Tulsa club weeks earlier. His death had a ripple effect throughout the Rockies organization and, of course, Major League Baseball.

There are varied opinions about coaches wearing helmets as they conduct their jobs just off the corner bases to the left and right of the foul lines.

Lee Tinsley, the Diamondbacks' first-base coach, said on Saturday, "If it was my preference, I wouldn't [wear it]."

But Flannery said it's no big deal.

"I've been wearing a skully inside the hat anyway, which worked just fine," Flannery said before the Giants' practice on Saturday at Scottsdale Stadium. "It was pretty scary. Last year there were a couple of times I had balls hit right at me. That's why I also wear cleats down there, so I don't slip when I try to get out of the way."

Hill also began wearing head protection during games after Coolbaugh's death. Hill was hit on the elbow by a line drive during Spring Training and had been mulling the option since.

"I think it's good any time we address safety issues that involve the game," Hill said. "I know there will be some coaches more comfortable with the way it used to be. It's going to take some adjustments on their part to get used to the new rule. But I think it's a good thing."

But Mike Gallego, the third-base coach for the Rockies, is not so fond of the new rule. Gallego, a middle infielder during his 13-year Major League career, including the American League championship seasons from 1988-90 in Oakland, said ingrained instincts make it much easier for him to react.

"I appreciate the concern," Gallego said on Friday. "We're obviously very vulnerable out there. It's something we obviously have to get used to. It's been a macho thing all these years not to wear some protection out there. So I guess I'm still a little caught up in that part of it. I can read the ball off the bat as good as anybody. So I'm not a big advocate of wearing the helmet, but I understand it."

Chip Hale, the third-base coach for the defending NL West-winning Diamondbacks, also asserted that it will take an adjustment.

"It's going to be a tough thing for us, because we're not used to it and we might feel a little uncomfortable," Hale said on Saturday. "I knew [Coolbaugh] very well, and his brother, [Scott], is one of my best friends, so I have no problem wearing it, especially every time I think of Mike and the dangers out there. I'm sure once we get used to it, it will just be commonplace."

Glenn Hoffman, of course, applauds the new rule.

"It's a good idea," he said. "If it helps only one person, it'll be worth it."

Coolbaugh joined the Tulsa Drillers on July 3, and his inexperience in the coaching box is cited by some as a possible cause of his untimely and seemingly random death. As a Major Leaguer, he played 44 games over two seasons for the Cardinals and Brewers as his on-field career waned during the 2002 season.

He was trying to balance his family obligations with his love of baseball, Rockies manager Clint Hurdle said at the time of Coolbaugh's death.

"He was a good man," said Hurdle, who had spoken with Coolbaugh before he took the job. "We had some common fabric. We talked about kids. We talked about the relationship, the demands of a father, of a coach. And he was so excited. He loved the game and his family."

The deadly play came in the ninth inning of that ill-fated game.

Other professional sports leagues have taken precautions. The National Hockey League mandated decades ago that all players and on-ice officials wear helmets and, more recently, that nets be installed in all NHL arenas high above and behind the goals. The latter rule was enacted after a 13-year-old fan was struck by a puck during a game at Columbus, Ohio, on March 17, 2002. She died three days later.

Prior to that incident, no fan had ever died in this manner at an NHL arena. And likewise, although Major League Baseball is taking its own protective measures, coaches getting hurt during games by batted balls have not been commonplace.

Baseball was slow to mandate the wearing of batting helmets by hitters at the plate. Even though Cleveland's Ray Chapman died after being beaned by Yankees pitcher Carl Mays at the Polo Grounds on Aug. 16, 1920, it wasn't until 1971 that wearing batting helmets at the plate became mandatory.

And at least one current coach believes that MLB mandating coaches to wear helmets in play came too late.

"It's too bad they waited until someone was killed," said Astros first-base coach Jose Cruz Sr. "But we'll do what we have to do. It's good for all the coaches. A lot of the guys have come close to getting killed."