Michael Conroy/Associated Press

I first met Carson Palmer 13 years ago. He wore khaki pants and a white button-down shirt with pinstripes. He was fresh-faced and clean-shaven. In his eyes was the glint of promise that you see in a man who is about to accomplish great things.

He was supposed to become the Bengals' version of Troy Aikman. It didn't turn out quite that way.

The quarterback who walked off the practice field and into the locker room on a recent October day wearing No. 3 for the Cardinals was a different quarterback than the one who wore No. 9 for the Bengals. The thermometer showed 106 degrees in Tempe. Palmer's cheeks were ruddy, his jersey soaked with sweat. "You never get used to the heat," he said.

He might never get used to it, but he has learned to deal with it. He was feeling the heat way back in middle school, when he was the quarterback for the Mission Viejo Cowboys. He was without peer in the Junior All American Conference, and he was expected to prove it with every throw. The heat became more intense when he was a high school junior at Santa Margarita, fielding offers from the likes of Notre Dame and Miami.

Winning the Heisman Trophy at USC and becoming the first pick in the 2003 draft turned up the heat further. Expectations in Cincinnati may have been higher than anyone could have reached. After his team lost the only playoff game he started and finished, garbage was dumped and smeared in his front yard. Then, on the prestigious occasion of reaching 20,000 career passing yards, Palmer was booed in the stadium he called home.

After seven seasons as a Bengal, he came to the conclusion he needed to move on, so he told the team he didn't want to play there anymore. He still is feeling the heat from that bold decision.

Palmer is wired ideally for the exaggerated swings that typically chart a quarterback's life. While he is obsessed with being the best quarterback he can be, he can flip the switch at the end of the day.

"Football is great and I love it and I'm so fortunate and blessed to be able to do it," he said. "But I wholeheartedly believe I'm not defined by what I do on the football field. I'm defined by the father I am, the husband I am, the family member I am and the impact I have on others."

His perspective helped him through some dark days in 2006, when football could have been taken away from him. On a gruesome low hit in a playoff game, he tore his anterior cruciate and medial collateral ligaments, suffered cartilage and meniscus damage and dislocated his patella.

Perspective was necessary again last fall when Palmer tore his ACL a second time, just when he was hitting his stride with the surging Cardinals. He thought he was on the verge of accomplishing something special and lost it all in the moment he heard the horrid pop in his knee. As the cart he was being carried on drove slowly off the field and up the tunnel at University of Phoenix Stadium, he held up his head and gave the thumbs up, but he was barely keeping it together. That night, he wept bitterly.

All of it was preparing him for now.

Why come back?

Palmer has a great life away from the game. He has a beautiful wife, Shaelyn, who was the starting goalkeeper for the USC soccer team. They have three children, six-year-old twins Fletch and Elle and four-year-old Bries. He has a passion for hunting white-tailed deer. He enjoys fishing and shooting hoops, and he's a single-digit handicap golfer.

Why come back?

Palmer has been one of the most well-paid players in the history of his sport. He's made tens of millions of dollars. Money long ago ceased to be a motivator for him.

Why come back?

Palmer career stats Year Tm Yds TD 2004 Bengals 2,897 18 2005 Bengals 3,836 32 2006 Bengals 4,035 28 2007 Bengals 4,131 26 2008 Bengals 731 3 2009 Bengals 3,094 21 2010 Bengals 3,970 26 2011 Raiders 2,753 13 2012 Raiders 4,018 22 2013 Cardinals 4,274 24 2014 Cardinals 1,626 11 2015 Cardinals 1,155 10 pro-football-reference.com

At the time of his injury, he already had thrown for more passing yards than all but 21 quarterbacks. He is the only player in history to have 4,000-yard passing seasons for three teams. In 2005, he threw more touchdown passes than anyone. He had a passer rating of 100 or better in nine straight games in 2004 and 2005, one of the best stretches in league history. He played in two Pro Bowls and was voted MVP of one of them. He had been an accomplished quarterback.

Why come back?

Three years ago, Palmer's lung was punctured by broken ribs in a road game against the Panthers. Doctors told him he needed to stay in a Carolina hospital for three days. It was late on Dec. 23, and getting home for Christmas was Palmer's priority, so there was an alternative—insert a tube in the lung to allow drainage on the flight home. Palmer took the long flight from Charlotte to Oakland with a hole in his side and a bag in his hands.

The thumb on his throwing hand once appeared to be sticking straight out of his wrist. Surgery corrected that. There was a broken collarbone, a torn ligament in his elbow, nerve damage in his shoulder and another punctured lung. And the two knee reconstructions.

Why come back?

He heard the question frequently, from fans, friends and even people who didn't know anything about him. He saw it on social media. He heard it in stores, restaurants and airports.

And it annoyed him. Pissed him off, really.

What they could not comprehend is Palmer's deep love of what he does. And it's not just playing that he loves—almost every player loves the games.

"I love Sunday night after the game—you win, you go to the parking lot, you grab a beer, hang out for a little bit," he said. "Then I can't wait to get home and watch the game on my iPad. I love getting in Monday, and I can't wait to see what the team we are getting ready to play is doing on third down. I love the studying, the preparation, the mental challenge of turning around on a Monday. I love the practices. Obviously the games. I love being in the locker room. I love all of it."

And what the people asking that question didn't get is Palmer has been in pursuit of one thing his entire adult life, and he wasn't ready to abandon the chase.

"There is only one thing left for him," Cardinals receiver Larry Fitzgerald said. "It's winning a championship. And he understands he has a ballclub that is capable of doing that."

Palmer never has been part of one postseason win. He wants to feel what it's like to advance to the second round of the playoffs, then to a championship game. He wants to go through a two-week schedule to prepare for the biggest game of his life. He wants to feel the rush of knowing he can put his signature on a game that will be talked about for football eternity.

"I want that experience, selfishly, so badly," Palmer said.

In July, Palmer posted a remarkable Instagram video of his knee transformed from scarred and battered to nearly normal. And he quoted Thomas Edison: "Many of life's failures are people who did not realize how close they were to success when they gave up."

Palmer will not be one of those people.

Palmer has been told by someone who should know that Feb. 7, 2016, will be one of the best days of his life. Shaelyn is expecting their fourth child on Super Bowl Sunday. What a day it could be.

Palmer's younger brother Jordan Palmer has been around the block a few times. He hung around the NFL as a backup quarterback for seven seasons, including the better part of three seasons playing behind Carson in Cincinnati. He also has worked with scores of athletes in his role as a quarterbacks consultant, currently for Elite 11.

He said his big brother is the hardest worker he ever has been around.

"And this offseason was the hardest I've ever seen him work," Jordan said. "It's a crescendo."

At 35, Carson understands that he is nearer to the 19th hole of his football life than he is to the ninth. He isn't committing to anything beyond this season, but he is committing entirely to this season.

"I think my realization that the window is closing and my career is not going to go on for a long time, that has changed a little of my approach," he said. "I've always been pretty intense, but I think everybody gets to that point where you realize, man, I only have a couple left. That definitely has changed me a little bit."

Palmer trained every single day during offseason. From post-surgery through training camp, he took not one day off. His typical routine—lifting, agility work, sprinting, rehab and throwing—lasted about seven hours. Palmer's backup, Drew Stanton, trained with him in San Diego and said halfway through workouts they had to change shorts because they were so soaked with sweat.

"I think a lot of guys make a mistake of training less as they get older," Palmer said. "I think the older you get, the harder you have to train. Maybe you don't train as long, but the intensity goes up."

Most 13-year veterans wouldn't concern themselves much with mechanics. Palmer, under the direction of his brother, reevaluated the way he was throwing. Jordan, who has been catching passes from Carson since he was two and Carson was six, discovered Carson was tilting his shoulders forward and subsequently overstriding. He came up with a series of drills to break down his muscle memory, he said.

Now, Cardinals wide receiver John Brown testifies that his quarterback's arm is stronger than it was one year ago.

Carson's commitment to being the best he could be went beyond training. He pre-planned every meal through the entire offseason. He went on a rigorous diet that eliminated carbs except for one day each week. He increased his fluid intake to the point of getting IVs. He regularly checked his blood and took vitamins to ensure all of his levels were on point.

"He is as meticulous as anybody I've ever been around as far as his preparation and taking care of his body," Stanton said.

After coming to Arizona with a 54-67 record as a starter, Palmer has won 16 of his last 19 starts. His record is the best of any quarterback in the NFL over that time period. Palmer had a career passer rating of 86.3 coming into this season. Through four games, his passer rating is 106.4. He is on pace to throw twice as many touchdown passes as his career average.

His coach, Bruce Arians, believes Palmer is playing as well as any quarterback has under his watch.

Michael Conroy/Associated Press

"He is so healthy now, and he spent so much time building not only the knee but his entire body," said Arians, who also has coached Peyton Manning, Ben Roethlisberger and Andrew Luck. "His arm is live. His legs are so strong with all the rehab he did. And he has a great understanding of what we're trying to get done."

The presence of Arians clearly is a factor in Palmer's enhanced ability. Jordan Palmer cited Arians' willingness to drive the ball downfield, the freedom he gives Carson to get the Cardinals in the right play with the right protection, and the way Arians utilizes each of the wide receivers to his strengths.

"This situation suits him better than any other he's been in," Jordan said.

Carson has the physical wherewithal to take advantage of Arians' system and, perhaps more importantly, the mental wherewithal. He sees things and understands things the 25-year-old version of himself never could.

A shelf in one of Palmer's closets is filled with Mead spiral notebooks. There are about 24 of them—two for each season he has been in the league. Each notebook is dated and filled with carefully written notes from Palmer's studies of one of his seasons. There are notes about his decisions and his throws, what he did right, what he did wrong. There are notes about the offensive system that season and the defensive schemes he opposed. There are notes about down and distances, about red zone, short yardage and more.

That's a lot of information on a shelf. And Palmer knows what to do with it. Early in his career, Palmer struggled to integrate what coaches were trying to teach. Knowledge didn't always translate to touchdown passes. Over time, he figured out on his own that he was a visual learner.

"I'm not a guy who can sit there and look at a diagram of a play and understand it," Palmer said. "I tried note cards for an entire year. Draw up a formation, flip it over. X has got this. This is what happens if it's this coverage. This is what happens if this guy is hot. I tried writing it over and over again, drawing it over and over again. I tried quizzing it, having my wife read off plays and I would go through my checks. None of it worked. I need to experience it. I need to see myself do it, I need to see it on the practice field, I need to watch myself in game films."

Through the years, he also learned how to watch game tape efficiently. Early on, he found himself focusing on the quarterback instead of on the defense he was opposing the next week. Now Palmer thoroughly dissects his opponent every Tuesday and typically reports to work Wednesday with an exhaustive list of 20 or so questions for his coaches. Arians calls him "the ultimate gym rat as far as studying film."

All of it helps explain how and why his abilities are culminating this season.

"I've been around a while," Palmer said. "I've been in a lot of different situations. I've grown from them all. I've learned from them all. You gain perspective. And luckily I play a position that your skills don't diminish when you get older as much as some other positions."

Any time Palmer is asked how he's feeling, he responds, "I feel old." It's a stock line, and an invitation to doubt.

When pressed, Palmer admits he feels pretty good, all things considered. His strength is at an all-time high. His energy level would shame many younger athletes.

The weekly recovery process is more difficult, however. Every Monday at 8 a.m., he has a standing appointment with his chiropractor, followed by an appointment with his massage therapist. It takes him maybe five days to feel normal after a game. Back in the day, he would spring out of bed on a Monday morning, shake off Sunday's hits and load his golf bag in the trunk.

He still has quickness in the pocket—Stanton believes Palmer has the best feet of any NFL quarterback—but Palmer said he no longer could get close to his best 40-yard dash time of 4.65 seconds. There had to be some price for two knee surgeries.

Ross D. Franklin/Associated Press

Injuries and years often change the person more than the athlete. In the course of talking about knee injuries, I told Palmer about my 14-year-old son tearing his ACL not long ago playing football.

"That's going to shape him," Palmer told me. "It will be great for him. He won't realize it and he won't want to hear it. But in 2017 or 2018, he can look back and say I went through something and conquered it and I'm a better person for it."

Palmer knows. Jermaine Gresham was Palmer's teammate in Cincinnati in 2010, and he has reconnected with him this year in Arizona.

"He is more relaxed now," the tight end said. "He is wiser. He is more focused in. The reason is he has built resiliency through all the hard times."

See, through all the hope and heartbreak and individual success and frustration, Palmer was becoming as much as being.

I last met Carson Palmer a week ago. He was wearing a black jersey and red shorts that exposed scars on his left knee—a big one and a little one, and a few blades of grass. His face looked chiseled and was covered with stubble, with some specks of gray. In his eyes was the glint of promise that you see in a man who is about to accomplish great things.

Dan Pompei covers the NFL for Bleacher Report.