Kelvin Benjamin was supposed to be the superstar of this 2015 Carolina Panthers team. Instead, as he recovers from an ACL injury, he's watched their magical season unfold from the most bittersweet seat in the house.

CHARLOTTE — The real challenge, Kelvin Benjamin learned quickly and almost cruelly, comes on game days. As the party rages on in Carolina this season, and the undefeated Panthers turn the league into their own personal showcase, Benjamin watches it all unfold from the best, most bittersweet, seat in the house.

So close, and yet so far. That’s the stark reality the second-year Carolina receiver faces these days, after his late-training camp ACL injury rendered him a spectator for the NFL's success story of the year. Benjamin isn’t just missing a season, he’s missing the magic carpet ride of a lifetime.

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Thirteen games have produced a franchise-record 13 wins for the Panthers this season, and who knows where this wildly unexpected saga is headed from here? Perhaps all the way to Santa Clara, Calif., and a golden anniversary Super Bowl, with history in the offing. Few ever saw that potential for the Panthers without Benjamin in the lineup, but week by week it looks more plausible all the time.

Each season, there’s an invisible and yet unmistakable line in every NFL locker room separating the injured from the active, and only players truly know how different their existence feels depending on which side of the divide they occupy. As an injured veteran starting quarterback once told me almost two decades ago, “the train keeps moving, always moving, in the NFL, and once you step off it, even if it’s for a week or two, you get left behind.”

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Benjamin’s transformation in Carolina from dangerous lead receiver to determined head cheerleader was almost instantaneous, but he has remained steadfast in his commitment to absorb and experience as much of the team’s dream 2015 season as he possibly can, with a fresh scar on his left knee and a slightly pained smile on his lips. Always implicit in the NFL’s vaunted “Next man up” mantra is a man going down, and the ratio never changes.

“It’s been hard on him, it really has,” Panthers fifth-year head coach Ron Rivera said Monday, a day after Carolina improved to 13–0 and locked up a first-round bye in the NFC playoffs with 38–0 destruction of division rival Atlanta at Bank of America Stadium in downtown Charlotte. “You watch him and you see that longing to be out there on the football field, you really do. I can tell just from afar how much he’s hurting.

“Like [Sunday] when he was on the sideline with us. I just happen to see him standing over there watching the offense, and I could just see him cross his arms for a second and kind of exhale. Then I saw the shoulders drop and the head tilt (down). I just knew, ‘Ah, he just wishes he was out there.’”

“Sundays are the toughest day to get through. Those are the worst days. Seeing all the success the guys are having, you can’t help but be so happy. But at the same time, you feel like, ‘Dang, I wish I was out there.’” —Kelvin Benjamin

Whatever internal battle ensues with Benjamin as he sees Carolina’s weekly joy ride continue, he isn’t going to let 2015 be entirely about loss, or miss out on what might be the best season of his career—even if that year won’t show any trace of his on-field impact.

“It’s tough, it really is, because I’m always used to being on the field, and being somewhat in the limelight,” Benjamin said Monday afternoon, taking a break from his rehab routine. “Sundays are the toughest day to get through. Those are the worst days. Seeing all the success the guys are having, you can’t help but be so happy. But at the same time, you feel like, ‘Dang, I wish I was out there.’

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“I knew we had a great team this year, even in camp. I knew it was going to be something special. It’s hard to feel like you’re not contributing to the team, not able to help. But now that I’m at the games, and hanging around the guys, and in the (post-game team) pictures, it seems like I’m more a part of it. (Sunday) I had so much fun. Being at that game, it felt like a party. The whole stadium was rocking. That’s why I’m hoarse now, because I was out there screaming so much. It was crazy.”

But game days still feel like a party he’s invited to, but only to watch from the sideline. No dancing allowed for Benjamin this season.

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After a spectacular rookie season in which Benjamin, Carolina’s first-round pick in 2014, led the Panthers with 73 receptions for 1,008 yards and nine touchdowns, he blew out his knee on Aug. 19 on a non-contact play in training camp, during a joint practice with the visiting Miami Dolphins. He underwent surgery on Sept. 10, just three days before Carolina’s season-opener at Jacksonville, and said early on in his rehabilitation he found it difficult to even watch his teammates play. While still on bed rest, he could only take seeing what he was missing for just so long.

“I would only watch them bit by bit,” Benjamin said. “I started off not being able to watch the whole game, because it was too painful for me. I love the game that much and I wanted to be out there with my team. I would actually watch the game on my cell phone, so I could turn it off when I wanted to turn it off, and then turn it back on when I was ready again. I’d always keep up with the score, but I would flip from live to just watching the stats.”

Benjamin said he would watch the Panthers game on TV and identify the signals quarterback Cam Newton gave before the play, then find himself mentally back on the field, running the route that would have been his to execute. Habits years in the marking do not break easily that first time.

“At that point I still knew the signals, and I would just go through the play in my mind,” he said. “Sometimes I could have thrown a signal back at Cam and it would have changed the route, and would have changed the outcome on that play.”

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But no amount of mental gymnastics could change the reality that his season was over even before it began, and that after being one of the centerpiece performers of the NFL’s record-setting 2014 rookie receiver class, his second season in the league would be spent watching, waiting and healing, while he targets 2016 for his comeback.

“The lowest point for me was once I got carted off the practice field,” Benjamin said. “Everything’s running though your mind—oh, your career’s going to be over, your season’s over. I had like 10 minutes in the locker room by myself, and I kind of knew at that point that I was done. At practice, they moved on. They don’t even stop the whole practice for you. That was the lowest point, just knowing that it was all over for me this season. Knowing that was the reality.”

Adding to the loss his injury represented, Benjamin, 24, had been dominating throughout Carolina’s training camp this summer, after enduring an uneven offseason of work that had been interrupted by lingering hamstring issues. Rivera attributed some of those problems to the 6-5, 240-pound Benjamin carrying too much weight on his frame, and the former Florida State star showed up to Panthers camp in Spartanburg, S.C. determined to change the narrative.

“He's got to find a way to stay part of it, and then we've got to try and make him feel like he is a part of it.” —Ron Rivera

“Coming out of OTAs and minicamps he had struggled with the hamstrings, and I had made a comment, ‘Well, maybe his weight had a little bit to do with it,’” Rivera said. “He came back to training camp and it was the best shape he had ever been in. I mean he was killing people in camp. Even (top Carolina cornerback) Josh (Norman) was struggling to cover him. And then to have him get hurt the way he did, and so late in the preseason, it was so disappointing.

“It’s unfair, but there’s nothing a kid like Kelvin can do right now. He’s got to heal up, he’s got to bide his time. He’s got to find a way to stay part of it, and then we’ve got to try and make him feel like he is a part of it.”

Rivera had a nine-year NFL playing career with the Chicago Bears (1984-92) and said the only time he missed a couple weeks due to an injury was during his rookie season. But even then, he felt the no-man’s land that every injured played enters in the NFL, especially in his own locker room. It’s a well-defined chasm between the ready-to-go, and those who can’t help the cause.

“You do feel it, absolutely,” Rivera said. “And part of it is you feel like people are looking at you, like, ‘Oh, okay, right.’ Nobody is like that with Kelvin because he proved himself last year. But I think it’s also what drives some of these guys with the whole injury thing, with guys having to play hurt. They’re trying not to be on the other side of that invisible line. But I think in this case it’s going to increase Kelvin’s desire to get back out there and make things happen next year.”

Panthers receiver Jerricho Cotchery, a 12th-year veteran, has never missed a season due to injury, but he speaks for every NFL player when he describes the loss of routine that a sidelined player experiences.

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“I know for myself, missing even two games, it kills you,” Cotchery said. “When you’re hurt and we have that away game, sometimes you don’t travel. So you have to sit at home and watch, and your Sunday is not like a typical Sunday. There’s a sense of isolation there, not being involved. On Saturday, you’re like, ‘They’re probably in meetings now, or they’re getting up on Sunday and going to the stadium.’ And when you’re watching it on television, you’re not able to connect with those same emotions. That’s tough. I’ve experienced that a couple times and it’s a difficult process.”

If there was one consensus opinion once Benjamin went down, it was that Carolina’s passing game was doomed and had just lost its most irreplaceable cog. No one looked at the rest of the Panthers receiving roster and thought the likes of Ted Ginn Jr., Cotchery, second-round rookie Devin Funchess, Philly Brown and Brenton Bersin would be enough to complement Newton’s productive connection with Pro Bowl tight end Greg Olsen. Besides Benjamin, receiver Stephen Hill also suffered a season-ending ACL injury this summer. But somehow, through it all, the Panthers have thrived on offense, with Newton elevating his game and becoming the favorite to earn league MVP honors and Carolina scoring a league-best 411 points (31.6 per game).

“He’s handling it very well. I think he’s helped us out tremendously this year in a lot of ways, but not in the ways he expected to help us out.” —Jerricho Cotchery

Apparently Benjamin was an early believer, even when others saw limitations.

“I kind of figured we’d be fine, because of how this team was built,” he said. “Some teams rely on their No. 1’s at every position way more than their other players, but it wasn’t like that for us in camp. Everybody was eating. When they brought Ted (Ginn) in, Ted brought speed that I’ve never seen before. I knew once this team got its confidence, it would be crazy to (beat). Once the guys bought into the idea that it doesn’t matter who makes the plays, we went on a run.”

The Panthers’ run actually started in December 2014, when they won their final four games after a dismal 3-8-1 start, finishing 7-8-1 and winning a second consecutive NFC South title, the first team in the division’s 13-year history to manage that feat. A playoff win at home against Arizona in the first round, followed by a competitive divisional-round loss at Seattle whet the Panthers’ appetite for more in 2015.

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Plenty more has unfolded thus far this season, with Carolina’s 17 consecutive regular-season wins being the most recorded in the NFC since the conference’s inception in 1970. Benjamin’s contribution has been limited to being an extra set of eyes, and another voice in the room. It’s all he can offer until 2016.

“I’ve tried to encourage him to just focus in on what he can do,” Cotchery said. “I think he’s done a great job of that, especially the way he’s attacked his rehab, seeing him in there every morning, same time, ready to work. But it definitely makes it tough after the way he came to camp. The reality is nobody could cover him in camp. The focus he had each and every day was impressive.”

So too is Benjamin’s resolve to not wallow or pout about his ill-fated 2015. The face of the Panthers is undeniably Newton, but Benjamin has made it his goal to add to Carolina’s heart and soul as this remarkable season unfolds.

“He’s always encouraging us, just telling us how excited he was watching the last game and what we were doing,” Cotchery said. “And when he’s been on the sidelines, it’s been the same thing. He’s handling it very well. I think he’s helped us out tremendously this year in a lot of ways, but not in the ways he expected to help us out.”

When the calendar flips in a few weeks, Benjamin will be as ready as anyone in Carolina to greet 2016. Not only for what the postseason might hold for this year’s unprecedented Panthers squad, but for the promise of his own fresh start. His comeback is already in the making.

“I just feel like this is my job right now, getting ready for 2016 and supporting this team,” Benjamin said. “I’m going full throttle right now. I’m not the type to mope. I’m going to take this year and I’m going to let Cam know, ‘I’m going to be ready for ’16. I love what you guys have going this year, but I’m going to be ready for ’16.’”

In Carolina, as this charmed season continues, Benjamin’s bittersweet game days are numbered.