The scar starts at the edge of Drew Mehringer's temple and curves along the left side of his head, covering about five inches. It serves as a reminder of a freak accident, a near-death experience and, ultimately, a life-changing event.

Mehringer, 28, was hired as Rutgers' offensive coordinator in December, nearly eight years after he suffered a head injury that left him in a coma for three days following an emergency brain surgery. When he awoke, there was a week of uncertainty about the potential long-term mental and physical effects.

"It was 10 days of pure hell," Mehringer's father, Eric, said in a phone interview with NJ Advance Media.

In what Eric refers to as a miracle, Drew pulled through completely healthy. Granted a new lease on life, Mehringer emerged from the hospital with a newfound sense of purpose.

"It was a tremendous learning experience for me," Mehringer said in a phone interview with NJ Advance Media. "Obviously it's not the way you want to learn anything, but it was a very cool moment in my life to realize how short life is and you're not promised tomorrow at any moment."

'THIS IS WAY WORSE THAN WE THOUGHT'

A big music fan, Mehringer went through a classic rock phase while a student at Rice University in Houston. Mehringer and a friend, Will Shoppa, attended a Van Halen concert in Dallas on April 24, 2008.

Mehringer and Shoppa drove from Houston to Shoppa's house in Fort Worth, where they took a train to the American Airlines Center in Dallas. They were told by the conductor that the train would leave 30 minutes after the concert ended, so when the lights came up at the end of the show, Mehringer and Shoppa sprinted through the arena parking lot to catch the train.

"We were cutting through cars and things like that and they had these chains marking the parking lot and I didn't see one, so I hit it with my shin running full speed," Mehringer said. "When I hit it with my shin, I fell face first and hit my head on the concrete."

Mehringer doesn't remember anything after that point, but he later learned the details of the night. He got up and walked to the train while Shoppa, who played defensive end at Rice, initially made fun of his friend for tripping over the chain despite being a Division 1 athlete -- Mehringer, a quarterback, suffered a career-ending knee injury during his freshman year at Rice in 2006.

Shoppa quickly realized something was wrong with his friend, however.

"They thought that I had just fallen down and hit my head and at the worst of it had a concussion," Mehringer said. "But then I started to blackout and my buddy was like, 'That's not right.' "

Shoppa pulled the emergency chain to stop the train, which had already left the station.

"Will Shoppa, in my opinion, is the guy that saved Drew's life," Eric Mehringer said.

Paramedics came and took Mehringer off the train, but there wasn't an understanding of the severity of the situation because there were no visible signs of injury.

"They didn't even turn the lights on for the ambulance or anything like that," Mehringer said. "My buddy was asking in the front seat if he could turn them all on and they were like, 'Just shut up.' "

Fortunately for Mehringer, he was taken to John Peter Smith Hospital in Fort Worth.

"We were told if you have head injuries, that's the top people in the Dallas-Forth Worth area," said Eric Mehringer, who made the 20-mile drive from the family's home in Mansfield, Tex., to meet his son and Shoppa at the hospital. "It was all divine intervention, I believe, because they took him to the correct hospital unbeknownst what happened to him."

Doctors initially thought Mehringer had a concussion, but Eric sensed there was something more seriously wrong and asked the doctors to re-examine his son.

"So the lady feels around on my head and essentially finds the (fracture)," Mehringer said. "They were like, 'Oh no, this is way worse than we thought.' "

Mehringer had suffered a traumatic brain injury known as a contrecoup.

"If you can imagine the front right corner of your head, that's what landed first," Mehringer said. "What happens essentially is it sends a shock wave around your head in both directions and it met on the other side of my head. When the two shock waves meet, it fractures your skull because there's so much force going through it. So the fracture didn't break the skin, but it broke blood vessels underneath my skin in my brain, so it started to fill up with blood. Because the skin trapped it inside, it starts to fill up with blood and the blood starts pushing on your brain and it's rapidly killing you because your brain is not built for sustained pressure like that."

Mehringer arrived at the hospital at 12:30 a.m. He underwent an emergency craniotomy at 6 a.m.

"The doctors looked at me and said, 'If we don't do surgery, your son is going to die,' " Eric Mehringer said.

Mehringer said the doctors "had to open up my skull and drain the blood out and then piece my skull together."

Drew Mehringer

Mehringer was in a coma for three days after the surgery.

"They gave us four days to determine if he was going to live or die," Eric Mehringer said. "You get past that hurdle and you're thinking, 'OK, great, he's going to live. And then they give you the next bad set of news and it was, 'We don't know if he's going to be mentally or physically handicapped.' "

Racked with stress, Mehringer's parents went 65 straight hours without sleep. Finally, eight days into the ordeal, doctors told the Mehringers their son would be fine, mostly because he was young and in excellent physical shape.

"Proudly, I have the fastest craniotomy/contrecoup recovery in the hospital's history," Mehringer said.

'NO RESERVE. NO RETREAT. NO REGRET.'

Mehringer did some soul-searching while recovering in the hospital.

"You're sitting in there and it's this weird moment in your life where you should have been dead, but you're not," Mehringer said. "So you're like, 'I need to reevaluate everything in my life.' "

Mehringer read a story about the life of William Borden, a man who chose to become a missionary rather than inheriting his father's fortune in the early 1900s. Borden died of spinal meningitis at the age of 25 shortly after arriving in Egypt as part of his missionary work. After Borden's death, it was discovered that he had written six words in his Bible: "No reserve. No retreat. No regret."

"That resonated with me at that moment and stuck with me ever since," Mehringer said.

Mehringer used to write the motto on the back of his left hand every morning and he shaved his head on the anniversary of the accident each year. Now, he writes the motto in his journal every day and he no longer shaves his head each April.

The experience is still with Mehringer every day, but it has become more personal over time. The only outward reminder of the accident is the scar above his left ear.

Mehringer didn't decide that he wanted to be a college football coach when he was in the hospital eight years ago. But his outlook changed in a way that set him on his current course.

"I was a dumb 20-year-old running around acting like an idiot," Mehringer said. "At that point you realize, 'Oh my gosh, I need to pull my life together,' and 'What's the person I'm going to be?' At that point, I didn't know that I was going to be a college football coach, but I did know that kind of person, a person that's willing to give away his family fortune to go do something like the ministry is a tremendous way to think. From that standpoint, I was like, 'That's the kind of person I think I want to be.' It just came at the right time to dramatically change me as a person and the way that I think, operate and what my paradigm for living life is. So I feel very blessed from that standpoint."

Dan Duggan may be reached at dduggan@njadvancemedia.com. Follow him on Twitter @DDuggan21. Find NJ.com Rutgers Football on Facebook.