It was the bottom of the fifth inning and the 0-1 pitch was on its way, and the next sound you heard at Fenway Park was the deep thwack of a well-struck baseball. It was hit by Red Sox outfielder Shane Victorino, a line drive heading straight up the middle, toward the big man on the mound, a pitcher disguised in a small forward’s body.

Somehow, in the milliseconds it took for the ball to arrive, Brandon McCarthy’s mind raced at a pace equal to the ball, the thoughts loaded with dread and disbelief: No, this can’t be happening. No way.

Not again.

Victorino’s shot came last Aug. 4, on a sunny Sunday against the Diamondbacks, McCarthy’s club before he was traded to the Yankees last week. It also came just 11 months after the 6-7, 200-pound McCarthy was on the receiving end of an infinitely more horrific thwack, after he got drilled by a shot off the bat of the Angels’ Erick Aybar while pitching for the Oakland A’s. The date was Sept. 5, 2012, in the fourth inning in Oakland amid the heat of a pennant race, and it was as nasty a head blow as a pitcher has sustained in recent memory, one that resulted in a fractured skull, a brain contusion and an epidural hemorrhage, the trauma requiring potentially life-saving brain surgery later that night.

And now, in his first start back from the disabled list, a month after he suffered a seizure in a Phoenix restaurant, Brandon McCarthy was seeing another baseball rocketing towards his head at 100 or so mph.

“The one (Victorino) hit back at me missed the same spot by about a quarter-inch,” McCarthy says. “That screwed me up for a little while, just because it makes it very real again. To that point, I hadn’t really considered it. (But) there’s some subconscious thought that just exists, just like if you get into a car accident or anything, once your brain has a negative outcome tied to something, it exists there.”

Brandon McCarthy, a 31-year-old from Colorado, is one of baseball’s more unguarded and thoughtful souls, and one of its leading Twitter humorists, often going back and forth with his wife, Amanda. When he returned home after the Aybar beaning, he tweeted, “WELL IF BEING DISCHARGED FROM THE HOSPITAL ISNT THE BEST TIME TO ASK ABOUT A THREESOME THEN IM FRESH OUT OF IDEAS.”

Shortly after McCarthy collapsed his long body just in time to avoid being nailed by Victorino’s missile, Amanda tweeted:

“If you would have ducked like that last year you would only have like 50,000 twitter followers.”

Now on his fifth major-league team, McCarthy has a career record of 45-60, with a 4.19 ERA. He never set out to be the poster boy for the perils of pitching, but then, he never expected to be hit, either. No pitcher does. Not Herb Score, the brilliant young Indians lefthander who was never the same after being hit by a line drive off the bat of the Yankees’ Gil MacDougald in 1957. Not the Blue Jays’ J.A. Happ, who was skulled by Tampa Bay Rays’ Desmond Jennings last May, or Jennings’ teammate, Alex Cobb, who was hit by a drive by the Royals’ Eric Hosmer last June.

“We always feel we’ll be able to get out of the way,” Cobb says. “I was definitely one of those guys. Maybe we just talk ourselves into that — that we’re quick enough and our hands are good enough and that it just (won’t happen) to us.”

With the fresh and chilling images of a spate of recent incidents — don’t forget the Reds’ Aroldis Chapman getting crushed in the left eye in spring training by a rocket hit by the Royals’ Salvador Perez — the issue of pitcher safety is commanding more attention than ever before, all the more so with the Padres’ Alex Torres recently becoming the first big-league pitcher to wear a protective hat in a game. Torres, then with the Rays, came on in relief of Cobb the day he was hit, and has never forgotten. Ron Darling, for one, thinks the alarm and new-found vigilance is a good thing.

Darling never got hit in the head with a batted ball, but he did get a major scare in Montreal once, losing a shot off the bat of Tim Raines in the yellow seats behind home plate at Olympic Stadium.

“It was the only ball in my whole career that I didn’t see, and it scared me,” Darling says. The ball hit him in the chest. The next pitch he threw, he said he recoiled as the batter swung — another career-first. And then he said the urge to recoil passed, Darling attributing it to the same blind confidence Cobb spoke of.

“”It’s complete hubris,” Darling says. “You have that DNA, that gene, that says, ‘Well, I could’ve fallen out of the window, but I didn’t, so bleep you.’ There’s a real Darwinism or macho thing to it . . .where (you think), ‘I’m more powerful than you.’”

It will take a lot to penetrate the hubris, Darling says, but it must happen. Players are bigger, and stronger, he said. The latest generation of pitchers often do not work on their fielding as much as pitchers once did, so it makes them less proficient as defenders, though in the most frightening of instances, even Ozzie Smith could not get his glove on a liner back to the mound. Indeed, the ball that hit Cobb was clocked at 102.4 mph.

Says Darling, “If you take an infielder — say David Wright — and you asked him to come over here and stand sideways, 55 feet from home plate, and then said, ‘OK, now I’m going to give a guy a fungo bat and hit the ball at you as hard as he can’ — there is no way he would do it. Nobody would do it.” And for a very good reason.

When you put all of your exertion into a pitch and fire toward home plate, even if you have the mechanics and polish of Greg Maddux, you are a proverbial sitting duck.

Or as Zach Wheeler of the Mets says, “Every pitcher has been hit somewhere at some time.”

* * *

It was six months ago that the special hat worn by Alex Torres received official approval by MLB. It’s called the isoBLOX Protective Cap, and only after it met the MLB-mandated standards — offering protection against baseballs traveling at least 83 mph — did it pass muster. The big-league cap, according to Bruce Foster, CEO of 4LicensingCorp., the parent company of isoBLOX, is rated for 85 mph in the temple region, and 90 mph in the forehead. The protection comes from padding the company describes as hexagon-shaped “plastic injection molded polymers combined with a foam substrate” that is designed to diffuse impact through both absorption and dispersion. The same technology is used in an isoBLOX skull cap that the company is marketing to youth players; that product fits beneath a regular cap, and is available at Dick’s Sporting Goods for $59.99.

The big-league caps are about a half-inch thicker in the front than a regular cap, and about three-quarters of an inch thicker in the sides, and weigh about seven extra ounces. Foster says that about 60 big-league pitchers have ordered them, though only Torres is using them in games, for reasons both pragmatic and aesthetic. To many, Torres looked as if he’d stumbled off the set of E.T.

Former Met R.A. Dickey tried it in spring training and found it heavy and unwieldy. Current Met Dillon Gee has never tried it, and doesn’t plan to. “I just don’t like the way it looks,” Gee says. “It looks uncomfortable, looks heavier. I never even really thought about wearing it.”

You would think that pitchers such as Cobb and McCarthy would be the first to sign on, but neither has.

Cobb is a spokesman for isoBLOX, endorsing the use of the skull cap for all youth players. But when you see him on the mound for the Rays, you will see him in a regular Rays cap, not the specially designed model with the padding stitched in by New Era.

“The most obvious guy who should be out there wearing it would be me, but right now it’s just not suited to my high-maintenance needs,” Cobb says. “I’m extremely picky out there on the mound. Everything has got to be just perfect for me out there, and right now in my career to make that big of an adjustment to a bigger cap is just a little difficult.”

McCarthy consulted with the company through its design process, but wasn’t on board with the prototype that earned MLB-approval.

“There were heat issues. There were size issues. It was just too much to overcome at that time,” McCarthy says. “I’ll always be interested in the other versions that come along, but that one right there wasn’t ready.”

Foster acknowledges that the current model “is not perfect. We’re back at the lab right now. We need to get it a little thinner. . . . There’s vanity and there’s protection, and we just have to close that gap.” He thinks that widespread adoption is not far off.

“Clearly, there is a need for it,” Foster says. This is to save someone’s life.”

* * *

Both Cobb and McCarthy believe that head protection for youth-league pitchers — whether it’s Little League, Cal Ripken, Babe Ruth League — should be mandatory. Considering that Little League pitchers are just 46 feet from home plate, and the hitters are swinging metal bats, it is hard to argue.

“We make the hitters wear helmets, so I don’t see any reason why (pitchers shouldn’t, too),” McCarthy says. “I’ve gotten to meet a lot of kids in the past few months who suffered the same injury, a lot of them. If it avoids just one of them having something like that happen and the hell that wreaks on a family, I’m all for it.”

Says Cobb of the skull cap, “It’s not cumbersome to the child using it. It’s an easy transition phase for young players. I think it’s an awesome idea that will make the game safer on the youth level.”

As for when the day will come that protective pitching caps are commonplace — or even mandatory — in the big leagues, most agree that the trend, across all sports, is heading that way. The days of Babe Ruth hitting his majestic blasts without a helmet, or Bobby Orr rushing up ice with his hair blowing behind him, are gone. First and third base coaches wear helmets now. Ron Darling still can’t fathom that catchers just used to wear a hat beneath the mask, recalling when the Red Sox’ Bob Montgomery had the revolutionary idea of using a thin piece of plastic instead.

Says R.A. Dickey, “If you follow the evolution of the headpiece in baseball it points to growth in greater head protection. I’m not saying it will be mandatory in the next five years, but as better ones come out, with a more refined design, then more guys will choose to wear it.”

Brandon McCarthy, the unwitting poster boy for the issue, doesn’t disagree. He will make his next Yankee start without any protection on his head, no matter the near-fatal hit he took on Sept. 5, 2012, and the scare he got from Shane Victorino 11 months later. Next year, or the year after?

Who knows?

“I think (protective hats for pitchers) will be commonplace at some point,” McCarthy says. “It’s just a matter of the technology and the functionality merging together. The reason I don’t wear it is I don’t think it’s there yet, I don’t think I’s ready. Alex Torres thinks it is, so there are going to be people that make that individual decision. There are going to be other companies that come through and really try to hammer it down, to make a piece that everybody gets on board with because it just makes sense to wear something. But it has to fit what you’re trying to do as a professional. I do think it will be something that happens.”

— With Mark Feinsand and Kristie Ackert

* * *

HITS JUST KEEP ON COMING

Since Brandon McCarthy took a line drive off his head off the bat of Angels’ Erick Aybar on Sept. 5, 2012, three other pitchers have had similar incidents. Here’s a look:

J.A. Happ

When: May 7, 2013

Team: Toronto Blue Jays

Hit By: Desmond Jennings of the Rays

What happened: Taken off the field on a stretcher. Received a head contusion and a laceration to his left ear.

Alex Cobb

When: June 15, 2013

Team: Tampa Bay Rays

Hit By: Eric Hosmer of the  Royals

What happened: Taken off the field on a stretcher,  spent the night at Bayfront Medical Center in St. Petersburg with a concussion. Was out for about two months.

Aroldis Chapman

When: March 19, 2014

Team: Cincinnati Reds

Hit By: Salvador Perez of the Kansas City Royals

What happened: He was taken off the field during game with a slight concussion and had surgery to repair broken nose and bones above lef t eye. Was out for two months.

— Bridget Scaturro