For coaches, players and fans, the final month of the 2014 Eagles' season was difficult to endure. But Matt Barkley, better than most, was able to put it all in perspective.

The backup Eagles quarterback, after all, had learned how to survive suffering from one of the world's leading authorities.

In 2009, while a Southern Cal freshman, Barkley met and befriended Louis Zamperini, the ex-Olympian whose almost unimaginable World War II horrors were the basis for the phenomenal best-seller Unbroken.

"He spoke to our class - we all had no idea who this old guy was," Barkley said. "But pretty soon everything stopped and we were all listening intently. I'd never heard anything like his story. Afterward I stayed to meet and talk with him."

An unlikely friendship developed between the college QB and the aging war hero, a USC alum who had finished eighth in the 5,000 meters at Hitler's 1936 Berlin Olympics.

"We ended up doing different events together around L.A., lunches and that kind of thing," Barkley said. "He really began to encourage me. I hadn't done anything at USC yet, but he knew I was starting as a true freshman, and he offered me words of encouragement that helped me get through that difficult year.

"That was really special. He didn't have to do that. I hadn't done anything at USC. At that point I was a nobody and yet he took the time to invest in me and lift me up."

Not surprisingly, Zamperini, who died of pneumonia at 97 last July, just months before December's debut of the big-budget film on his life, stressed the need for mental discipline, lessons that were reinforced when Barkley reached the NFL in 2013.

"Louis, in my mind, embodied what it means to push through your mental limits and even the physical limits of what your body can handle," recalled Barkley. "He was so mentally tough. He reminded me a lot of how [Eagles coach Chip Kelly] is always emphasizing that. Chip brings in all these Navy Seals and Ph.D.s and sports psychologists and others to talk about mental toughness and the need to challenge yourself."

Barkley pressed the older man for details of his remarkable life, the focus of the Laura Hillenbrand book that spawned the current movie of the same name. So compelling is Zamperini's story that four-plus years after its publication, Unbroken remains No. 1 in sales of e-books and paperbacks and is No. 5 on the hardcover list.

A hardscrabble California kid who turned his life around through long-distance running, Zamperini was a WWII bombardier on a B-24. In April 1943, eight crewmates died when it crashed into the Pacific. Zamperini and another crewman survived on a raft for 47 days in shark-infested waters.

After washing ashore on a tiny island, they were captured and taken to a prison camp in Japan. For two years there, Zamperini suffered regular beatings and sadistic degradation at the hands of a camp officer, Mutsohiro Watanabe. He endured again and after the war became a committed Christian who spoke around the world, sharing his tale of hope and faith.

Barkley said Zamperini told him his religious conversion occurred in the chaotic moments that followed the plane crash.

"He said that when the plane went down and he was tangled up in wires under water, he made a promise that if he escaped he would commit his life to God," said Barkley, himself a Christian. "He said he recognized that he'd been saved by a miracle because he blacked out and then, all of a sudden, was moving toward the surface."

While starving and adrift on the vast ocean, and later in the Japanese camp, Zamperini used various mental exercises to shift his focus and to exercise his brain.

"He said he did things like reciting recipes and trying to recall all the meals he'd ever eaten," Barkley said. "He stayed mentally sharp to the day he died. He would recall details from when he was my age like it was nothing. He was a really good example to me of the power of mental toughness. He overcame all those hardships by staying sharp and having faith in a greater power."

Despite their difference in age, the two men corresponded regularly. They grew so close that in 2010 Zamperini invited Barkley to his home to watch the U.S.-Canada hockey match at the Vancouver Winter Olympics.

"He was like 92 then, and he was amazingly sharp," Barkley said. "Sometimes he would go off on tangents, and his hearing wasn't that good. You could ask him about one thing, and he'd answer about something completely different. But we chatted quite a bit. He told me how he'd spoken to Hitler after the 5,000. He showed me the Nazi flag he'd stolen while in Germany, and the torch he carried in the relay [preceding the 1998 Olympics in Nagano]."

While in Japan for those Games, Zamperini publicly forgave his captors, even Watanabe. An American TV network tried to arrange a meeting between the two men, but the former Japanese officer refused.

"I almost think Louie's whole postwar story is more of a testament to what kind of man he was than what happened during the war," Barkley said. "He didn't shy away from his captors. He went back, and he forgave them. For the rest of his life, he talked about his experiences in the most humble way possible. He didn't do it to bring glory to himself but to lift other people up.

"He had more grit than anyone I've ever met. He mentored so many boys and young men, and I was just fortunate to be one."