TALLADEGA, Ala. -- Restrictor-plate racing presents a different set of variables for NASCAR officials, particularly when it comes to policing aggressive driving. And that was more than evident Friday at Talladega Superspeedway when Sprint Cup Series director John Darby warned drivers to tone down things after at least five cars were damaged in a crash just minutes after the start of the first practice session.

"Typically, the first seven laps off the truck, we don't tear a bunch of stuff up," Darby said. "We react to those kinds of things, and a bunch of wrecked race cars that early in the weekend doesn't make sense."

That incident concerned Darby enough to let everyone in the garage area know that NASCAR wasn't going to let things get out of hand.

"For a long time now at Daytona and Talladega, we've warned the drivers about aggressive driving," Darby said. "We will do that again [Sunday] for the race. More importantly, what doesn't make sense is to let aggressive driving go unnoticed or with no reaction in practice, where everybody's there to shake their cars down and get them ready for the race. To ignore that and have the potential to have a big wreck in practice, where all the teams have to go back and scramble for backup cars didn't make sense.

"So what we saw early on in practice [Friday] was that everybody was getting a little carried away and at the start of the second practice, we warned them to relax a little bit, do what they needed to do and stay off the aggressiveness."

The last two restrictor-plate races have ended in wild, last-lap crashes. The last time the series visited Talladega, Carl Edwards and Brad Keselowski made contact, with Edwards' car eventually winding up in the catchfence. At Daytona in July, Kyle Busch crashed hard after sweeping back across Tony Stewart's fender as the two battled for the win, with Kasey Kahne then rear-ending Busch.

With a drop in horsepower caused by a shrinking of the diameter of the holes in the restrictor plates, speeds have decreased. But the unintended consequences are that drivers must become more aggressive in their efforts to make passes, or pull away from the pack. And that's something Darby and his crew will be keeping a close eye on in Sunday's Amp Energy 500.

A steady cold drizzle Saturday morning forced officials to cancel qualifying, which means points leader Jimmie Johnson and second place Mark Martin will lead the field of 43 to the green flag. It also means many of the faster cars will be deep in the pack at the start, which could make for increased bump-drafting early.

"If you look at pushing, the bump-drafting, the blocking, if you look at all of that, the cars stand a lot better chance of staying under control and more straight if a little of that goes a long way," Darby said. "What we did see [Friday] was a couple instances of somebody pushing a car, bump-drafting and getting carried away with it too deep into the corner where the front car actually got sideways. It's Talladega. You expect a little of that here. We'll watch that like we always do [Sunday] during the race. Hopefully we won't have to make a call, but if it gets too obnoxious, we will."

Darby is less concerned with cars working together to bump-draft on the long backstretch or in the tri-oval. What does concerns him is when someone gets bumped when they least expect it.

"It's fine when everybody's going in a straight line, and nobody's dancing or moving around," Darby said. "But if you get into the turns and hit somebody too hard or steer somebody too hard, it's just a huge potential there for a bad wreck. Again, in most cases, if you get the right partners together and they both understand each other and what they're doing, it can happen without incident. It's when the uninvited pusher or pushee gets involved, and they're not so good at it, is when you have problems."

What's harder to determine is blocking, when one car intentionally moves up or down the track in an effort to maintain its position.

"That's the only way to keep someone behind you sometimes," Edwards said. "If you look at the blocks that have happened at the end of the race and how it's turned out for the guy blocking, that's kind of self-policing in a way. It's really easy to get turned around blocking.

"The guy in front has a responsibility to make sure he doesn't swipe across the guy's hood, and the guy behind, I believe, has a slight responsibility to give the guy a little bit of room and let him try to defend his position. But I'd hate for NASCAR to have to make a judgment call to say, 'Hey, they blocked once,' or 'They blocked twice.' I don't think we need that. I think we can do it ourselves as drivers."

Ryan Newman agreed.

"Yeah, blocking is a part of this sport," Newman said. "Blocking is a part of racing here more so than most race tracks even more so than Daytona. It's frowned upon by most drivers but there are a few drivers that try to take advantage of the situation. Also I'm happy that NASCAR doesn't intervene with blocking as other series have intervened because I don't think that's necessary. I think the drivers are fully capable of managing their situations. Having NASCAR let us manage those situations is as equally as important."

And from NASCAR's point of view, Darby said the sanctioning body won't step in unless it's perceived as blatant.

"I guess you've got to define blocking, which is tremendously hard to start with," Darby said. "The policing of it is just as hard. Other forms of motorsports have tried to police it, and they can't. They screw it up. Unless it's obnoxious to the point where there's not much doubt, it's just a tough call to make."

Kevin Harvick's car wound up needing an additional pass through technical inspection Saturday after the team damaged one of the brackets that supports the rear wing.

"It's not a technical violation," Darby said. "Part of the process of setting the wing angle is you've got to loosen the lock bolts first. The team made a small error and forgot to loosen the locks and as they attempted to adjust the wing, they actually damaged the wing bracket. No harm, no foul, but the process of going back and correcting everything is basically what you'd do for [initial] inspection."

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