In a segment of the Chiefs practice field, players alternate running full speed and crashing into a weighted bag. The drill is just about as old as the sport itself, surviving innovation and sprinkling to every age of youth, high school and professional football.


The intent is to simulate a tackle, all the while knowing there's little replication for the real thing. Best they can do, though.


For now. On Thursday night at Arrowhead, after an offseason absent tackles and hard hits, the weighted bags transform to ball-carriers on the move. With instincts to dart away from the contact or the power to fight through it. They're shifty. They're acrobatic. And believe it or not, they are not quite as keen on being wrapped up as a tackling dummy.


Without a preseason schedule, the Chiefs — and other NFL teams — are about as least prepared for it as they've ever been.


"No question my number one concern," Chiefs defensive coordinator Steve Spagnuolo said. "We've tried to simulate it as much as possible. We don't have a lot of live periods -- we do a little tackling that way. I think the coaches, the assistant coaches, have done a great job getting it done as best they could."


There has long existed the narrative that offenses possess a bit of an advantage in the opening week. Or at least they should. After months to institute new plays, they hide them from the tape. A defense, therefore, must react on the fly.


The lack of live game action — which would offer players the chance to hit someone — only furthers that notion. The Chiefs will give rookies their first NFL snaps on Thursday. Linebacker Willie Gay and cornerback L'Jarius Sneed, in particular, could see a lot of playing time. They've never before faced NFL competition.


"It's going to be tough, man. Obviously not being able to have preseason games (and) we missed a good portion of the spring. I think tackling at this level is tough on its own," Chiefs safety Tyrann Mathieu said. "A lot of these guys can make multiple people miss."


A segment of the Chiefs' search for a solution settled on video. It's not self-scouting. It's not even scouting Thursday's opponent, the Houston Texans.


It's film on the fundamentals.


"I don't know whether it will help or not. But every day we watch tape of tackling," Spagnuolo said. "I'm talking about good tackles, how to tackle. So maybe it's a visual thing. But it's a concern. We won't know until we get into the middle of the game and see how some of these guys react."


Tackling is more than good form. More than strength. More than wrapping up.


It requires instincts. It necessitates taking the right angles. Sometimes, it's about playing in accordance with teammates. That all revolves around timing, and that's one of the last elements to emerge after a quiet offseason.


"I think you (need to) have the ability to play fast, play to your leverage, use your teammates," Mathieu said. "I think all tackles aren't necessarily meant for you to make. Sometimes it's for you to use your help, and two guys bring down one guy. But as long as we can play fast, as long as we can play to our leverage, use our teammates, I'm hoping we'll be fine. But, yeah, I think it will be an adjustment early on. But as long as we're playing fast, I think we can make up for some of the mistakes we may have in the game."