Busch, who broke his right leg and left foot in a crash a day before the season-opening Daytona 500, spun nine minutes into the first practice session when he was bumped from behind by Brad Keselowski. As Busch's car spun down the track, he was hit squarely in the side by Greg Biffle.
Those two cars then spun into Martin Truex Jr., and the scrum was hit by Denny Hamlin. Also caught up in the crash was Carl Edwards, as Joe Gibbs Racing had three cars involved in the crash and 10 total drivers had to pull out their backup cars.
"Looks like (Keselowski) got into my left rear," Busch said. "He got away unscathed and trashed everybody else's stuff."
Busch placed the blame squarely on Keselowski for a move he deemed "not very smart."
"All these guys at the shop and everybody, they work way too hard building race cars in general to be wrecking them in practice. There's room to lift (off the throttle) and sometimes people don't," Busch said. "It's his fault. He caused it, but I've also been in the same boat and caused them before.
"It's practice, you don't need to be up a guy's left rear. I rolled out and got out of the gas I don't know how many times just to not run into the car in front of me because it's not that time of the game to go."
Busch was sidelined the first three months of the season with his injuries. He returned to his JGR team in late May, and NASCAR said he can participate in the Chase for the Sprint Cup championship should he qualify for the 16-driver field.
He took a big step toward that last week by winning on the road course in Sonoma, California, but he still must make the top-30 in points to be eligible. Busch came to Daytona ranked 37th with 10 races remaining to crack the top 30.
Busch is 136 points out of 30th and needs to average roughly a 14th-place finish in each of the next 10 races to hit his goal.
Busch ended the day — in his backup car — 16th on the speed chart following the second practice.
The session was led by Danica Patrick, who posted a lap at 198.133 mph as she paced all of her Stewart-Haas Racing teammates. The four SHR drivers sat atop the leader board, with Kurt Busch second behind Patrick and followed by Kevin Harvick and team co-owner Tony Stewart.
"It was pretty good in the last practice," Patrick said.
The four-car contingent from Hendrick Motorsports was next, with Kasey Kahne leading Jeff Gordon, Dale Earnhardt Jr. and Jimmie Johnson.
Ryan Blaney, who held his own at Talladega in May and finished fourth, was ninth in final practice and the fastest non-Chevrolet driver. The Ford driver was 39th in the Daytona 500 because of an engine failure.
Edwards, who went to a backup car after the earlier crash, rounded out the top 10 in a Toyota.