Some images are never forgotten. They're indelibly imprinted on your consciousness, which is what happened to Chiefs head coach Andy Reid earlier this year when he flew to Atlanta to visit safety Eric Berry, who was undergoing chemotherapy treatments for lymphoma.

"At about 2 o'clock he ran out of juice," Reid said. "I mean, it was just like, 'I need a nap.' That's going to open your eyes a little bit."

He had no hair on his head or face, and his eyebrows had fallen out, but it stuck with Reid that the former Pro Bowler had a single hair growing from his chin -- and that Berry refused to cut it.

"He's telling you, 'I'm going to play. I'm going to get back and be better than what I was. I'm going to do this,'" Reid said, "and you're looking at him going, 'All right, we'll see.'"

Last weekend, on the one-year anniversary of his diagnosis -- and four months after being declared cancer-free -- Berry showed again that he's serious about making good on his promise. He did a little bit of everything in a 33-3 demolition of the Chargers, lining up at deep safety, squatting on zone responsibilities in the flat and playing off-man coverage in certain situations. Once, he slipped past two blockers to ruin a potential big gain on a screen pass.

His return to the field, and continued ascension to elite status, is among the more remarkable stories this season. On some levels it's almost incomprehensible what Berry put his body through to get here such a short time ago. An example: Try working out twice a day between chemo treatments.

A cruel offseason

"The treatments, even for elite athletes, can be tiring and physically draining," said Dr. Stephen Wang, chief of oncology at Kaiser Permanente South Sacramento Medical Center in Sacramento, California. Wang did not treat Berry, who turns 27 next month. But he has witnessed the side effects of cancer treatment.

"Most uniquely, one of the drugs can affect the lungs and cause shortness of breath and coughing," he said. "Because of that, treatment often impairs performance. So what he's doing is quite unusual and quite remarkable."

Arizona coach Bruce Arians showed his support and respect with a "Be Berry" T-shirt in Week 14. AP Photo/Matt York

Tony Villani, the owner of XPE Sports in Boca Raton, Florida, has trained Berry in every offseason since 2010. When Berry walked into the building in May, he was about 15 pounds lighter, had no hair and his face was sunken. But what Villani remembers more than that: Berry still had his infectious smile.

Villani decided to go easy in their first workout. No full-out sprints or power training, just jogging and functional mechanics. Berry wasn't pleased. He didn't come to be babied. He had pushed his body as far as he could on his own, sometimes needing one or two hours afterward to gather himself. In Villani, he wanted someone who could get him to the next level.

"Let's go. We gotta get it," Berry said. "I've got to get back with my teammates because there's something special we need to do."

"We had to get right into sprint training and power training and football drills," Villani said. "We'd do about an hour and a half or two hours starting at about 8 in the morning. After the first day, I wasn't even going to tell him to come back, and he said, 'What time do you need me back here?' I told him to come back at 4. He was there at 3, doing extra stuff on his own."

San Francisco 49ers receiver Anquan Boldin was the only other NFL player at the facility at that time. Boldin prefers to train away from the team during the offseason, so it basically was him, Berry and Villani.

"Tony and I were talking about how we couldn't believe the stuff that he was going through at that time, yet still coming in and working out like he had never been away," Boldin said. "He wanted to go all-out from the beginning. Just seeing the way that he was working, you could tell that he was determined to get back on the field and be back to his normal form. Usually people that go through chemo, they're physically drained. They don't have a lot of energy. But you couldn't tell with him."

The trio was together for two weeks, after which Berry returned to Atlanta for his final chemo treatment. When he returned to south Florida to continue training, the facility was full of NFL players who had completed their team workouts and were preparing for training camp.

"We had Anquan, Mark Ingram, the Pouncey brothers, Marcus Gilchrist, Pierre Garcon, Brandon Flowers, Kareem Jackson, and they were all talking to me on the side saying, 'Tony, do you think you're overdoing it on him? He's doing more than we even do,'" Villani said. "I said, 'You know him. I don't know if this is what he physically needs, but it is what he mentally needs. He wants to mentally know he's doing more than anyone else, even after chemo.'"

Even so, the Chiefs brought him along slowly, in part because of what Reid saw on his visit to Atlanta. He knew Berry's intentions were good, but the former University of Tennessee star hadn't played in a game in 10 months. His mind might be willing, but what about his body?

An uneasy return

The Chiefs brought him off the bench in a Week 1 win over the Texans, with Berry recording two tackles and a pass breakup. He started the next week in a loss to the Broncos and finished with four tackles but no impact plays. The next four weeks were much the same. He was solid but unspectacular. No takeaways. No big hits.

Oct. 25 against the Steelers started much the same way, with Berry unable to capitalize on an opportunity to make a momentum-shifting play. After one instance, outside linebacker Justin Houston got on him.

Eric Berry hugged his mom, Carol, before a preseason game this August. AP Photo/Matt York

"There was a pass that I thought he had a chance to make a play on and he didn't," Houston said. "He made the tackle, but he should've had a pick. I told him, 'You hesitated, bruh. Don't think. Just go.'"

Houston and Berry have a close relationship. He knows that Berry isn't interested in being good. He wants to be great, which is why he asked Houston and others to critique his performance with the same unblinking honesty that he uses to grade himself.

Later in the game, Berry allowed his reflexes to take control when a ball slipped off the hands of wideout Antonio Brown. The ball appeared headed toward the turf before Berry burst and dove headfirst for the interception, then hopped up and returned it 15 yards. His first takeaway of the season set off a mass celebration among his teammates.

"He's been flying around since then," Houston said. "The speed of the game is so fast when you've been away that you have to adjust. Each week you could see he was getting there, but he was just a step from making the [big] plays that he normally makes. He always says he has high standards, so I hold him to high standards."

Berry followed that interception with another one two weeks later. And Sunday, against the Chargers, he had a season-high eight tackles. The game was significant for the team because it marked the Chiefs' fourth consecutive win and improved their record to 5-5. But it was particularly important to Berry because it came a year to the week after he was diagnosed with cancer.

The three-time Pro Bowler plans to be an advocate for cancer research, but for the next couple of months he wants to focus solely on football. Diverting his attention to the start of his 12-month journey might take away from his edge, so he chooses not to discuss it. He will tell his story in his time, at his pace. There already are plans to meet with at least a half-dozen cancer patients in South Florida after the season, and his foundation is raising money to assist with cancer research. But that will be then.

For now, he's trying to create his own indelible memory -- hopefully one that involves a Lombardi Trophy.

"I was going to do whatever I could to get back to this point to be right here with my teammates," he said late Sunday afternoon. "I told them before the game: I put my life on the line to be right here with y'all. Y'all helped me get to this point. So, it is what it is. We're just going to keep going forward from there. To me it's not a game. It's bigger than that."