DAYTONA BEACH, Fla. (AP) - DAYTONA BEACH, Fla. (AP) -- It took about 10 minutes to wreck several cars at Daytona International Speedway on Friday. Matt Kenseth triggered a five-car accident in the opening practice for the Sprint Unlimited, the non-points race that kicks off the season. Kurt Busch, Carl Edwards, Mark Martin and Juan Pablo Montoya also were involved in the crash. Busch's No. 78 Chevrolet sustained the most damage, forcing the team to switch to a backup car for Saturday night's exhibition event. Edwards and Martin also went to backups. "It's tough," Busch said. "A lot of hard work goes into these cars, and six weeks of preparation can be trashed in six laps." Kenseth took blame for the melee, saying he didn't see Busch gaining ground inside his No. 20 Toyota on the 2 1/2-mile superspeedway. "That was 100 percent driver error, my driver error," Kenseth said. "I had no idea anybody was there and he had a run at the same time and I came down in front of him and he couldn't get slowed up from staying out of me. It was a hundred percent my fault." The accident came less than 10 laps into the first practice of Speedweeks. It was supposed to be a learning session for NASCAR's redesigned race car, the one dubbed "Generation 6," and a preview of next weekend's Daytona 500. Instead, it turned out much like a test at Daytona last month. Dale Earnhardt Jr. caused that big one when he turned Marcos Ambrose, causing a 12-car wreck that essentially ended the three-day session. Teams returned to the track this week in hopes of learning more about the new cars, which have been tweaked to more closely resemble those that are in manufacturer showrooms. They also have different driving characteristics. The biggest issue, especially for those teams with damaged cars, could be a lack of inventory. NASCAR's development process took time, and outside vendors struggled early on to keep up with demand. That left several teams, including some of the big-budget ones, trying to play it safe at a track where side-by-side, bumper-to-bumper racing at 200 mph usually leads to massive collisions. Hendrick Motorsports driver Kasey Kahne predicted at Media Day on Thursday that practice would be conservative. "There is definitely a shortage of cars right now," Kahne said. "There may not even be an Unlimited practice because nobody ... we can't lose a car. We lost that one at the test, which you don't expect, so we need to make it through." It didn't happen -- at least not for the five teams involved. The wreck caused several teams to sit out the second practice session Friday night. "As soon as we saw one wreck, I think everybody was going to play chicken and not go out much after that," defending event winner Kyle Busch said. The season-opening event used to be called the Budweiser Shootout. NASCAR changed the name this year along with the entry rules. The sanctioning body went back to race's roots, inviting pole winners from the previous season and former event winners who raced at least once during the previous season to enter. The result was a made-for-TV event that included five former Cup champions and nine former Shootout winners in the 19-car field. Five-time series champion Jimmie Johnson, four-time champion Jeff Gordon and three-time champion Tony Stewart are in the field. So are two-time race winner Kevin Harvick and fan favorite Dale Earnhardt Jr. Reigning Sprint Cup champion Brad Keselowski, though, didn't earn a spot in retooled race. "I think any driver that's not in a race is disappointed to not be in it," Keselowski said. "I think it limits some of your ability to win the 500, not all of it, but some of it. But at the end of the day, this is not tee ball. Not everybody plays. We didn't earn our spot; we don't play. Pretty simple. "We spent our time and energy working on what we could to do to win a championship, not winning a pole. Quite frankly, if I had to choose between being in the Shootout or winning the championship, I would take the damn championship a hundred out of a hundred days." The 75-lap race will be divided into three segments, and fans were given unprecedented say in determining aspects of the format. NASCAR is holding open voting to determine what kind of pit stop, if any, teams will be allowed to make after the first, 35-lap segment. Fans also can decide whether two, four, six or no cars are eliminated after the second, 30-lap segment. But none of that should affect the bottom line, which is getting better prepared for the Daytona 500. "I think it is going to show how the cars are going to draft and how they are going to run," Montoya said. "I'm glad I'm in it."