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LONDON — They rode through the gray London afternoon, the coach and two former Pro Bowl players, their black Mercedes van rolling along the winding, narrow city streets. They were on their way to a practice field in the misty countryside, where cows and donkeys roamed nearby. It was Wednesday or—in the world of the Arizona Cardinals—Day 8 of the AP Era.

Bruce Arians sat in the first row of seats, silently reviewing the plays he planned to call against the Los Angeles Rams on Sunday in Twickenham Stadium. Carson Palmer was behind his coach, looking out through the tinted windows at school kids playing at recess in their dark-blue uniforms. And near the back was Adrian Peterson, his head buried in an iPad, his dark brown eyes intently scanning the screen. He was doing his own kind of schoolwork.

The van arrived at the practice field 15 miles southwest of London and out stepped the 32-year-old Peterson, wearing his red No. 23 jersey and red sweatpants, a smile on his face. It was the smile of a man at peace, a man eager for the coming day, the smile of a running back who only minutes earlier had learned he had been named the NFC Offensive Player of the Week for his seemingly out-of-nowhere performance last Sunday against the Tampa Bay Buccaneers.

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How unexpected were Peterson's 134 yards and two touchdowns on 26 carries? Consider that Peterson, who was acquired in a trade with New Orleans only five days earlier for a conditional sixth-round pick, hadn't rushed for more than 67 yards in a game in 22 months. What's more, the Cardinals ranked dead last in rushing yards in the NFL; the most yards an Arizona back had rushed in a game was 44 by Chris Johnson.

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And there was this: With Peterson lining up behind Palmer, it wasn't a coincidence that the veteran QB, who had been hit more times than any other quarterback in the league, was only pressured on a season-low 37.5 percent of his snaps, according to Pro Football Focus. With time to throw, Palmer looked like the MVP candidate he was in 2015, completing 18 of 22 passes for 283 yards and three touchdowns and one interception. Arizona finished with 432 yards of total offense, the first time this season it had topped the 400-yard mark.

"I feel like I've been reborn," said Peterson, leaning against a concrete wall outside of the England practice facility that doubles as a rugby training ground. "I need to touch the ball a lot to be at my best, and for whatever reason, I wasn't touching the ball in New Orleans. When I heard that I had been traded to the Cardinals, it was like all my prayers were answered, like a dream had come true."

"Adrian has totally changed our team," said Palmer. "Defenses were teeing off against us and I was getting hit. But with Adrian, everything is different. Defensive linemen can't pin their ears back and just rush the quarterback. They have to respect Adrian, and this will open up the field for us. He's as good as ever. I'm telling you, he's the Adrian of old. He hasn't lost anything."

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Arians knew he had to do something. Early in the morning of October 10—two days after his team had lost 34-7 to the Philadelphia Eagles and had rushed for only 31 yards on 14 attempts—he was driving his Cadillac Escalade to the team headquarters in Glendale when an idea popped into his head: What if we tried to trade for Adrian Peterson?

Arians walked into his office and flipped on his computer. Ever since running back David Johnson dislocated his left wrist in the season opener, an injury that likely will keep him out until at least Thanksgiving, the Arizona offense had sputtered. Johnson led the league with 18 touchdowns last season and gained at least 100 yards from scrimmage in 15 straight games, tying Barry Sanders (1997) for the longest single-season streak in NFL history. He was destined to be, according to most fantasy experts, the top fantasy player of the 2017 season.

In his office Arians watched every carry of Peterson's from 2017—even though there weren't many to see. In the season opener against the Vikings on a Monday night, Peterson, who split time with Saints veteran Mark Ingram and rookie Alvin Kamara, only played nine snaps. At one point late in the first half TV cameras caught Peterson exchanging hot words and glaring eyes with coach Sean Payton. The man known as "All Day"—the nickname given to him by his father when he was a toddler and ran around the house from sunup to sundown—wasn't happy being a part-time player.

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Peterson rushed for only 81 yards with the Saints in four games. But in his office, Arians saw flashes of the Adrian of old, the running back who was the No. 7 overall pick of the 2007 draft, the 6'1", 220-pound bell cow who was named All-Pro three times and a Pro Bowler six times in his first seven NFL seasons.

Arians needed to be convinced that Peterson was still the player he once was. Peterson missed 13 games last year with a meniscus injury, and Minnesota opted to not pick up an $18 million contract option to keep him, which led to Peterson's signing with the Saints in April as a free agent.

As Arians watched the film—he analyzed everything from his hip flexibility to his demeanor in the huddle—he liked what he saw. "The power and the aggression and the vision were there on the tape," Arians says. "He ran hard and could get something out of nothing. We had finesse backs on our team. I was looking for that power guy. He was it, brother, he was it."

After viewing Peterson on his computer screen, Arians immediately walked into the office of general manager Steve Keim, who then called Saints general manager Mickey Loomis. About 14 hours later, at 10:15 p.m. CST, Peterson was lying in his bed in his New Orleans home when he received a text message from a friend.

The text read: Did you get traded?

Confused, Peterson checked social media and was stunned to find out he had indeed been shipped to the Arizona desert—a place that has become a popular destination for NFL stars in the winters of their careers.

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He was on a plane early the next morning, flying first class to Phoenix. He was so consumed with learning the Cardinals playbook, which had been emailed to him, that he barely noticed liftoff and landing.

In his first practice later that Wednesday afternoon—a walk-through in which the players operate at quarter speed—Peterson went full throttle on each play. "It took one play in that walk-through for Adrian to show us that he's still a beast," says D.J. Humphries, a veteran offensive tackle on the team. "He went 100 mph right out of the gate. He raised the intensity level of the entire team. I was like, 'How could the Saints let this guy go?'"

After practice Peterson rode in a car with wide receiver Larry Fitzgerald, who invited Peterson to stay at his Phoenix guesthouse. The 34-year-old Fitzgerald and Peterson have known each since 2003, when they met at an awards banquet in Ohio. Fitzgerald told Peterson not to worry about day-to-day concerns such as grocery shopping and figuring out how to avoid traffic when traveling to and from the practice facility; Fitzgerald would handle all of that.

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"Larry has been so welcoming and just allowed me to spend all my free time learning the playbook," Peterson said. "His assistant helps with anything I need, and I just feel like I'm part of a family. The only way I can repay Larry is to work my tail off."

The first night in Fitzgerald's guesthouse, Peterson stayed up until 3:30 a.m. studying the playbook.

In his second practice last Thursday in Phoenix, the Cardinals went full speed in pads. The 37-year-old Palmer noticed something odd: He could hear Peterson run almost as clearly as he could see him. "The force he exerts is unlike anything I've ever witnessed," Palmer says. "When he makes contact with a defender, it's not a thud, it's a loud crack. You can even hear how hard his feet pound the ground. It's like in baseball when they say that when a great hitter connects with the ball, it just sounds different when the ball comes off the bat. That's Adrian. He just sounds different, still to this day."

Midway through practice Peterson took a handoff from Palmer—"He about ripped the shoulder out of my socket," Palmer said—and blasted between the tackles. He broke through an arm tackle, juked a linebacker, and then cut upfield in full thunder. "A young safety then was about to try to tackle Adrian," Arians says, smiling at the memory. "And I'm telling you, this safety was about to get trucked. So he just said, 'No, thank you' and moved out of the way. That's when I knew that Adrian Peterson was still Adrian Peterson."

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In New Orleans Peterson heard the whispers that he was washed up.

"I felt like my ability was going to waste in New Orleans," Peterson says. "The system just wasn't a good fit for me. But I still want to play four or five more years. I still can run a high 4.3 40. And I've always loved getting the ball deep in the backfield, which is what we're doing here. I feel like I'm built for this offense."

He sure looked like a perfect fit last Sunday at University of Phoenix Stadium. On his first carry—an eight-yard rumble up the middle in which he dragged two defenders the final four yards—the crowd gave him a standing ovation. He finished the opening drive with a 27-yard touchdown dash and gained more yards on the ground in that one possession (54) than the Cardinals had averaged in their first five games.

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Peterson displayed all his gifts on that opening drive—the power, the patience, the burst, the wiggle, the jump cuts, and the knees kicking high like lethal weapons. Palmer said that as his wife, Shaelyn, watched Peterson from their private box, everyone around her was in stunned disbelief, as if the football gods had mercifully rewarded her husband for all the hardship he had endured the first five weeks of the season. Peterson’s domination continued throughout the afternoon. For one game, "All Day" was back.

"Adrian will have just as big of an impact in our passing game as our running game," Arians says. "It's going to open up our play-action passing and everything else we do in the passing game so much."

But the question lingers: Can Peterson keep it going? In 1989, Herschel Walker ran for 148 yards in his debut with the Vikings after being traded from the Cowboys and then never approached that level of production again.

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Late in Wednesday's practice in London, Peterson looked like a man who understood the precariousness of last chances.

As Palmer zinged passes to trainers, as offensive linemen squared off in one-on-one drills, and as punter Andy Lee launched balls high into the wet sky, there was Peterson standing off to the side by himself. His head was down as he examined sheets of paper with complex play calls spelled out.

For three minutes, four, five, he never lifted his eyes. A horn blew. In a soft rain, the Cardinals players began walking toward the idling team buses, the practice over.

Alone, Peterson didn't budge.