HOUSTON -- As Adrian Peterson prepares to drive his legs forward, straining against the 430 pounds of resistance loaded into the cable attached to his waist, James Cooper tightens the wrist straps on his boxing gloves and readies his best shots. "If this doesn't get it out," Cooper says, "I don't know what to tell you."

Cooper pounds on the football tucked under Peterson's right arm, first with a series of heavy right hands, then with a flurry of rights and lefts as Peterson stretches the tension of the 40-yard rope. "Keep going, keep going," Cooper grunts, as he levies his final attempts to dislodge the ball from Peterson's grip. It does not move, and Cooper yields.

Peterson will complete 10 rounds of the exercise next week in one of the final workouts before he boards a plane to Minnesota and begins a season he believes could conclude right back here in the Super Bowl in 199 days. Peterson and Cooper have returned to the drill often in their decade of work together, but especially after the years when lost fumbles have hurt the running back's chances of reaching his first Super Bowl. They fixated on it after Peterson lost seven fumbles in the 2009 season and had a part in three during the Vikings' NFC Championship Game loss to the New Orleans Saints. During the 2010 season, Peterson's only fumble came when a teammate inadvertently kicked the ball out of his grip.

Fumbles By Season The number of fumbles and fumbles lost for Vikings running back Adrian Peterson in each of his NFL regular seasons. Year GP FUM LOST 2007 14 4 3 2008 16 9 4 2009 16 6 5 2010 15 1 1 2011 12 1 0 2012 16 3 2 2013 14 3 2 2014 1 0 0 2015 16 6 3

They return to it again to remedy a problem that resurfaced with seven regular-season fumbles in 2015 and one that left Peterson despondent following his fourth-quarter cough-up in the Vikings' 10-9 playoff loss to the Seattle Seahawks in January. Fumbling has not defined the running back's career, at least not to this point; both Eric Dickerson and Walter Payton fumbled on a greater percentage of their touches than Peterson has in his nine seasons. But it has helped end the seasons of perhaps the best two Vikings teams Peterson has played on, and he seems determined not to let it affect a third.

"Don't get me wrong: It was a heck of a play by those guys," Peterson said at his gym on Wednesday. "One (linebacker K.J. Wright) had my arm; the other (safety Kam Chancell0r) ripped the ball. It's not like it was punched out, or it was an easy give-up. They worked for it. But being able to have that arm pulled and still have that thing tight, or having the awareness to let your body weight go down and try to get your knee down, that could have prevented that. That's what goes through my mind."

In the days after the Vikings' loss, Peterson admitted he'd been too cavalier about his fumbles during the season, when he'd joked about how most of them had been recovered by his own team. He told former Vikings running backs coach Kirby Wilson -- who had chided Peterson about his technique -- that he was ready to take it seriously. And in the offseason, a technique tip arrived from an unlikely source: Peterson's old high school quarterback.

"He said, 'You know, Adrian, I’ve been doing some studying and watching your films and stuff, and I think I found out why you’re losing the ball,'" Peterson said. "Basically what it was, because I ran track -- that’s like my second love -- he’s like, 'Every time you run through, you already run high anyway, but once you get through the hole, you get loose with it. You gotta get away from that track mode, and that presents it for people to come in and punch it.'"

The 6-foot-1, 220-pound Peterson also knows there are more than a few NFL defenders looking for alternatives to corralling one of the game's fiercest runners. "When you've got people who are more focused on,'OK, I kind of don’t want to tackle him anyways; let’s find another way to slow him down,' they are focused more on punching that ball out," he said. "That's something I just have to realize and make sure I eliminate that."

Cooper is one of Peterson's partners at O Athletik and presides over a training group that often tops two dozen NFL players during the summer. Vikings defensive end Danielle Hunter has worked out there this offseason, and defensive tackle Tom Johnson and receiver Charles Johnson were among the players working out Wednesday. Buffalo Bills defensive end Jerry Hughes is there, as is Washington Redskins tight end Jordan Reed and Tennessee Titans safety Da'Norris Searcy. But in the final days before training camp, part of Cooper's focus will turn to Peterson and the young back who asked to train at his side this offseason: the San Diego Chargers' Melvin Gordon.

Second-year running back Melvin Gordon is trying to shed a reputation as a fumbler in San Diego. Jonathan Daniel/Getty Images

Before a left knee injury ended his season, Gordon had run for 641 yards in the Chargers' first 14 games. He'd also fallen into the same snare as the running back he grew up idolizing: Gordon fumbled six times last season, and while an offseason with Peterson presented two immediate benefits -- learning from his role model and being trained by the man who directed Peterson's famous rehab from knee surgery in 2012 -- Gordon discovered a third.

"I talked to Adrian about it, and he said, 'The biggest thing about the lack of ball security is, it's a mental thing,'" said Gordon, the Heisman Trophy runner-up in 2014. "You can do a lot of drills, but you can still go out there and mess up if you're not mentally focused on it. It's [having that reminder of], 'Someone's there. Someone's always there [trying to take it].'"

Peterson and Gordon took their turns fending off Cooper's punches, and a few verbal jabs -- "You might want to take off your little Mr. T. starter kit," the trainer chirped to Gordon about the gold chain he was wearing before the drill. Then, the two running backs shifted to a mat, where Cooper set up a drill he'd adapted from Brazilian jujitsu. Both backs tumbled over a balance ball, landing on their feet or placing a hand on the ground to steady themselves before rising and regaining their stride with a football still tucked under one arm, in a move designed to improve balance and awareness while going to the ground. This time, Gordon handled the drill more gracefully, while Peterson tended to charge the balance ball rather than decelerate and roll over it, leading to several stumbles.

"This drill busts his butt every time," Cooper said, "because he doesn't run like this. He's used to running a certain way, so this gets him out of it. That's why this is so dynamic: It makes an old dog have to learn new tricks."

For Peterson, before a season filled with opportunity to define his legacy, it might be more about eliminating old habits.

"[The punches are] more of an instinctual trigger than a hit," Peterson said. "It's kind of like going through that front line, where you've got arms coming, you've got legs coming. It really makes you clench on it even more and keep it tight."