It's extremely rare that any team is ever at full strength at any point of a 16-week season, and that looks to be the case for both teams when the Chargers host the Chiefs in the season opener.

Kansas City's perennial Pro Bowl safety Eric Berry is listed as doubtful with a heel injury, and Head Coach Andy Reid intimated he is highly unlikely to play.

Meanwhile, the Bolts know for sure they'll be without one of their biggest stars as Joey Bosa was officially listed as out with a foot injury.

However, it's not the same one that caused him to miss the preseason.

"He had a little bit of a setback on Wednesday," Head Coach Anthony Lynn said shortly after declaring him out. "It's a different injury, but it's going to be week-to-week … I was surprised. I was really surprised. I was looking forward to having him back like everyone else."

Perhaps no one else was looking forward to him returning to the field more than Bosa himself.

"He's very frustrated," Lynn continued. "He's been waiting for a while to get back on the field and he's doing everything he can. He just wants to be out there with his teammates, so yeah, he's pretty frustrated right now … It's football. It's always unpredictable sometimes. He was just on the field going through drills and that's when he felt it."

The good news is that the Chargers are more than confident in Isaac Rochell, the second-year defensive end out of Notre Dame who'll start in Bosa's place.

A star all spring during the offseason program, the 6-4, 280-pound 23-year-old picked up right where he left off when training camp rolled around. Even better, he was one of the Bolts' most consistent playmakers during the preseason. Rochell also started each contest in place of Bosa, earning valuable reps with the first-team defense that should pay dividends come Sunday.

For all those reasons and more, Lynn expressed supreme confidence in Rochell.

"Very confident in Isaac," he said. "Isaac had a great camp. He's grown like a weed. I told him it's a hell of an opportunity for him. I believe he'll step up and get the job done."

Meanwhile, Defensive Coordinator Gus Bradley noted earlier in the week that Rochell had carved out a valuable role on defense even before Bosa went down.

"Isaac Rochell has done a nice job for us," he said. "He got a lot of reps in the preseason and we're pretty high (with) where he is. Now, Ike was going to play anyway. So, I think that as a defense, we feel pretty strongly about the guys that we have in place."

Not that he needed any reassureance, but Rochell admitted after practice that it means a lot to him to have the backing and trust of his coaches.

"It always feels good to know your coaches have faith in you," he said. "When stuff like this happens, you don't want your coaches to feel like they're now in survival mode. You want them to be like, 'Alright, well the next guy's in. We have confidence in him, let's roll.' They definitely do a good job of telling me that, which makes me feel good about my play. But the biggest thing is during the week (of) practice. Practicing well to prepare myself."

The coaches aren't the only one impressed by the strides Rochell has made in the past year. In fact, at the end of June's minicamp both Bosa and Melvin Ingram went out of their way to praise their young teammates.

"I've always liked Isaac," Bosa said at the time. "I think he's a great guy and he has the potential to be a good rush end. The jump he made is kind of unexpected. Seeing him out here with his hands, the way he's moving, it's pretty unbelievable. He's doing a really great job."

"He's definitely making plays," added Ingram. "Ike's always been good. We always knew he could do it. And he's just showcasing his talent because he's been making so many plays. He's definitely going to be another piece to our rotation."

Now it's time to see that development play out when it counts most. And while Rochell knew he'd have an expanded role in 2018, he had no idea he'd end up being the starter for the season opener.

"I think the preparation, OTAs, training camp (and) going through all that, you kind of develop as your own player," he explained. "So when you go out and play, you just kind of do what you normally do. Again, the preseason starts definitely gave me the confidence of who I am as a player and let me develop myself as a 'starter.' I think the biggest thing for me was the preseason games. I knew I was going to be playing more so I guess it's just a title, not necessarily this huge new thing. But it is different, it is cool. I just have to do what I have to do and we all have to do our jobs."