The College Football Live crew marvels at Georgia running back Nick Chubb's ability to return from a knee injury so fast and to be able to perform at such a high level for the Bulldogs. (1:28)

ATHENS, Ga. -- It was a routine play, one Nick Chubb had run dozens of times as Georgia's workhorse running back.

Georgia was on the road at Tennessee on Oct. 10, 2015, one week removed from a humbling defeat against Alabama but still very much in the SEC East race. Chubb, a leading Heisman Trophy contender, took a toss on the Bulldogs' first offensive play. He landed awkwardly after being tackled and forced out of bounds.

"I remember how it felt when it happened," Chubb said. "There was a tingling feeling in my leg. My body went forward, and my leg went backward. I knew something was wrong."

Mike Worthington, who was Chubb's track and strength and conditioning coach at Cedartown (Ga.) High School, was sitting in the stands with his wife and Chubb's girlfriend.

"I was 20 feet away," Worthington said. "We were so close. I wasn't sure what happened. I thought he was caught in the chains."

But Worthington's wife, Libby, told him that Chubb wasn't getting up. Then someone texted him a photograph from the TV broadcast of Chubb's hyperextended left leg.

"It didn't look good," Worthington said.

Chubb, whose only previous injury had been a broken hand in high school, knew something was terribly wrong with his knee.

"I'm a running back," he said. "I thought I tore my ACL."

The next day, an MRI confirmed his injury was in fact much worse. He dislocated his left knee, tearing multiple ligaments and cartilage; only the ACL was still intact. Doctors kept him in an Athens hospital for nearly a week because they feared he might have nerve or vascular injuries in his leg, as well. Chubb would need season-ending surgery and faced months of rehabilitation. He wasn't sure when he would return to the field again.

Nick Chubb had surgery on his injured knee on Oct. 23, 2015. After a lengthy and intensive rehabilitation, he returned to the field on Sept. 3. Ron Courson/University of Georgia athletics

Because the injury looked so bad on TV, some even wondered whether Chubb would ever play again.

But, less than a year after undergoing surgery to repair three torn knee ligaments and cartilage damage, Chubb was back in the Bulldogs' starting lineup in the opener against North Carolina on Sept. 3.

According to the people who worked with Chubb during his rehabilitation, his quick return to the field is a testament to his determination and desire to return to the player he once was.

"Malcolm Gladwell wrote about outliers," Georgia director of sports medicine Ron Courson said. "Nick is an outlier. He's genetically gifted. He has a tremendous work ethic, and he's as mentally tough as anyone I've ever seen. I'm not surprised he's back."

Going into No. 12 Georgia's road game at No. 23 Ole Miss on Saturday, Chubb ranks second in the SEC with 365 rushing yards with three touchdowns. Even after suffering the knee injury, he's ranked among the top running backs available for next spring's NFL draft, if he decides to forgo his senior season.

"It's just something inside me, I guess," Chubb said. "I've never backed down from anything. I like challenges, and it was big challenge in front of me. I just wanted to come back for my teammates and everyone who supported me."

"I remember how it felt when it happened. There was a tingling feeling in my leg. My body went forward, and my leg went backwards. I knew something was wrong." Georgia RB Nick Chubb

In interviews with ESPN last week, Chubb, Georgia's coaches, medical director and others documented his 11-month recovery, offering a behind-the-scenes look at Chubb's long and painful rehabilitation and return to the field.

While Georgia fans and much of college football cheered his remarkable return, few realize the work and effort required during his recovery.

On Oct. 23, nearly two weeks after the injury, Chubb underwent surgery. Orthopedic surgeon Robert Hancock repaired Chubb's knee, along with James Andrews, the renowned surgeon who has operated on countless professional athletes, including NFL running backs Adrian Peterson and Todd Gurley and golfer Jack Nicklaus.

On a scale of 1 to 10, Courson described Chubb's injury as a 9. In addition to torn ligaments and cartilage, doctors also had to reattach the hamstring muscle in his left leg. In the weeks after his surgery, Chubb lost 20 pounds because of muscle atrophy.

"I always believed he was going to come back from Day 1, but it was a very, very significant injury," Courson said.

During the first four weeks after surgery, Chubb remained in the training room at Georgia's Butts-Mehre Heritage Hall nearly 12 hours each day. Since it would have been difficult for him to physically attend classes, he worked with tutors to maintain his academic work. His daily schedule included breakfast, four hours of rehabilitation, lunch, academic work and then strength and conditioning drills.

Chubb worked with a nutritionist to ensure he was eating enough protein to rebuild his muscles, and he spent time with a sports psychologist to cope with the shock of the injury.

"I knew I was going to miss the rest of the season, so I had to accept that," Chubb said. "I set short-term goals for myself and waited to see where it took me."

Initially, Courson worked with Chubb on improving the flexion of his left knee and rebuilding the quad muscle in his leg. Among other exercises, he bounced while sitting on a medicine ball and slowly sidestepped over small hurdles. Dry needles were poked into his injured leg to stimulate trigger points and relieve pain in his quad muscle.

Chubb missed the rest of the season after injuring his left knee at Tennessee. Skip Williams/AP Images

"After surgery, my leg was locked up and stiff for two or three weeks," Chubb said. "I couldn't bend it. I had to lie on my stomach while Ron was bending my knee. It was the worst pain I've ever felt. It was way worse than tearing it."

Before Chubb could run, he literally had to learn to walk again. He spent the first nine weeks after surgery using crutches and wearing a heavy post-operative knee brace. He faced a slow, painful recovery.

"You can't speed up Mother Nature," Courson said. "It's like baking a cake. You can't turn up the heat and speed up recovery."

Less than two months after surgery, Chubb was hitting significant milestones. On Dec. 19, he walked without crutches for the first time. He started leg extensions and ran on an underwater treadmill on Jan. 15.

Courson also used an experimental training method to help rebuild the muscles in Chubb's left leg. For the first time, Courson used Kaatsu blood-flow restriction training to help a Georgia player recover from injuries. Japanese doctor Yoshiaki Sato invented Kaatsu training in 1966, but it wasn't widely used in the U.S. until recently. U.S. skier Bode Miller used Kaatsu training to help him recover from a bad leg injury.

A thin, pressurized band was wrapped around Chubb's left leg to restrict the amount of blood flowing back to his heart. As a result, his injured leg was engorged with blood, filling his capillaries and muscle fibers while he worked out.

When Courson initially explained how Kaatsu training worked, he told Chubb that Georgia's trainers were going to push him until he reached muscle failure.

"Do you know what that means?" Courson asked him.

"No," Chubb said.

"He had never experienced muscle failure," Courson said. "Our biggest issue was slowing him down. Some people do rehab; he attacked rehab. I told him early on, 'Don't come in here and just do your time. Get everything out of it you possibly can.' He worked so hard."

Chubb gradually rebuilt strength and flexibility in his injured knee during the Bulldogs' offseason. Ron Courson/Georgia athletics

On Jan. 26, Chubb started walking stadium steps at Sanford Stadium -- the entire lower bowl. The next time, he did it while wearing a 20-pound weight vest.

Eleven days later, Chubb started straight-ahead running for the first time. With older brother Zachary watching, Chubb jogged 10 yards into the end zone at Sanford Stadium on Feb. 6.

The start of the 2016 season was only seven months away, and Chubb's knee was still extremely stiff. Not only was he not yet sprinting or cutting like a running back but he was still jogging with a significant limp. But running 10 yards was still a big step in his recovery.

"'We wanted him to visualize where he was going to be," Courson said. "Running in the stadium was where he was working to get back to."

In early February, Chubb started intensive proprioception drills to improve the stability and range of motion in his knee. While squatting, he balanced himself on a spherelike base while catching a medicine ball. While wearing hospital-type booties, he slid back and forth on a slick slide board, which hockey players use to build power and strength in their legs. He also worked on a cross-fit machine that downhill skiers use, as well as an ice skating trainer.

By Feb. 23, Chubb was jumping again on his injured leg. He started by jumping on both legs, then worked his way to only one leg. Eventually, he jumped rope and even used a pogo stick, once Courson found one with a 300-pound weight limit.

On March 1, Courson and his staff threw the kitchen sink at Chubb. He bounced back and forth between two bases that looked like medicine balls that were cut in half -- while catching footballs. Then he moved through a short obstacle course that required him to step over small hurdles and catch footballs while balancing on one leg.

"I don't know if we even have any guys on the team that could do that when they're healthy," Courson said.

Four days after Georgia opened its first spring practices under new coach Kirby Smart, Chubb started running change-of-direction drills for the first time. Chubb was held out of most team practices, other than taking handoffs and running short bursts in noncontact drills.

When Courson sent Smart a three-second video of Chubb running a cones course, in which he was cutting and sprinting between the cones, Smart replied: "Should he be doing that?"

"I didn't know," Smart said. "I really had no clue. Ron felt good about the surgery. The doctors thought it was a really good repair, but there was a lot of damage in there. I felt better after spring practice when I saw him taking handoffs and running straight ahead."

During the spring, Courson also introduced another unorthodox exercise to Chubb's rehabilitation: mixed martial arts and taekwondo. For the next five months, Chubb worked out three times a week with twin brothers Cole and Sean Borders of Borders Black Belt Academy near Athens.

Courson has worked out at the martial arts academy since the 1990s and thought the sport might break up the monotony of Chubb's rehabilitation. Initially, the brothers were hesitant to push him too hard. Chubb started by kicking heavy bags and paddle pads. He also did mat drills that focused on extending his leg and manipulating his knee.

"Once we started building up his strength and felt confident, we started using shields, and his body had to absorb a lot of the impact," Cole Borders said. "When Ron stopped coming with him, it kind of let us know that he was doing fine and we could open it up a little bit."

After a few weeks, Chubb graduated to tension kicks, a slow front kick that required him to hold his leg in the air, and push/pull kicks, which use resistance bands and wall anchors.

"Eventually, getting hit by one of his kicks was like getting hit by a Mack truck," Sean Borders said.

After spring practice ended, Chubb started working out with Georgia's track team. A track star in high school, Chubb worked with the Bulldogs sprinters to improve his speed.

Georgia's coaches certainly weren't worried about his overall strength. According to Courson, Chubb is still one of Georgia's strongest players. He squatted more than 600 pounds (strength coaches wouldn't let him lift additional weight), and he had the longest broad jump and heaviest power clean lift of any UGA player.

"Nick takes his body so seriously that he was never going to be out of shape," Smart said. "I think the guy was so aggressive in rehab that he came back stronger. He put on weight, and he's heavier. He seems just as fast."

By May, Georgia's trainers had cleared Chubb to participate in full strength and conditioning workouts without any restrictions. He was similarly cleared to participate in summer football workouts, such as voluntary 7-on-7 passing drills.

There was only one significant test remaining -- to be tackled at full speed. He would have to wait another three months for it to happen during preseason camp.

"There was just a little bit of doubt," Chubb said. "You really don't know. The last time I played in a game, my knee went the other way. You don't know if you're fine until you're falling and other people are falling on top of you."

When the Bulldogs opened preseason camp Aug. 1, Chubb was fully cleared to participate in all activities. Smart was going to be cautious with his star tailback, though. He allowed Georgia's defenders to hit and wrap up Chubb, but they weren't supposed to take him to the ground.

Finally, in Georgia's first full-contact scrimmage, on Aug. 13, Chubb ran the ball in live action on limited carries. On his first attempt, he was tackled quickly. On his next carry, he broke through the line and an official inadvertently blew his whistle.

"Coach, I'm all right," Chubb told Smart. "Tell them not to blow the whistle." After Chubb was given unlimited carries in Georgia's second scrimmage a week later, Smart was confident he would be ready for the season opener against the Tar Heels.

Smart was determined to keep Chubb's availability as quiet as possible, especially after running back Sony Michel broke his arm in an ATV accident July 4.

"We wanted to keep it in-house," Chubb said. "We didn't want people to get excited and put more pressure on me. People expect so much with everything you do."

Finally, on the Monday before the opener, Smart broke the news: Chubb was ready to play and wouldn't be on a "pitch count" against the Tar Heels. Chubb would soon find out that his new coach wasn't kidding.

Chubb rushed for 222 yards on 32 carries in his return to the Bulldogs lineup against North Carolina. Todd Kirkland/Icon Sportswire

Less than a year after suffering a devastating knee injury, Chubb started at tailback when the Bulldogs opened the season against North Carolina. On the game's first play from scrimmage, he took a handoff and ran for 6 yards. On the next play, he gained 13 yards and a first down. Just like that, Chubb was back.

"I never knew until the game actually started whether or not I was going to feel good," Chubb said.

In Chubb's first game back, he ran 32 times for 222 yards with two touchdowns, averaging 6.9 yards per carry in a 33-24 victory. Smart said he and his coaches never discussed how many carries Chubb would get in the game; they only decided he wouldn't get three or four consecutive attempts.

"None of the runs he had in our scrimmages looked like the ones he had against North Carolina," Smart said. "I think he was fresher. The thing you can't measure is how much better he makes everybody else around him. The fact he was able to play and be a captain really excited everyone else."

Chubb didn't have as much success running behind Georgia's revamped offensive line in his next two games. In a 26-24 victory over FCS foe Nicholls on Sept. 10, he ran 20 times for 80 yards with one touchdown. In last week's 28-27 win at Missouri in the SEC opener, he ran 19 times for 63 yards.

On Saturday, Chubb hopes to write the next chapter of his remarkable comeback story at Ole Miss.

"It's unreal," Smart said. "The guy is not normal. His heart beats to a different drum than everybody else. People like him eat challenges. He needs it, wants it and desires it. If you put something in front of him, he's going to handle it."