Epic disaster started on lap 66.
An electrical issue, which severely limited horsepower in the No. 42 Credit One Bank Chevrolet, forced Larson to make an unscheduled stop and he fell three laps back -- below the all-important cut line for the playoff elimination.
Ten laps later, Larson's motor blew and took with it his championship hopes.
At least, that was the assumption until three straight cautions shuffled the field dramatically, including an 11-car wreck that eliminated two playoff contenders.
Seven-time Cup Series champion Johnson started the final stage on the wrong side of the playoff-elimination cut.
His hopes took a massive hit on lap 188 when he got loose coming off turn four, sending the No. 48 Lowe's Chevrolet skidding across the frontstretch landscaping.
Johnson, who was running 10th at the time, restarted 27th but spun again before getting up to minimum speed, bringing out another caution.
During that restart, Truex's Furniture Row teammate, Erik Jones, got loose off turn two and took out Jamie McMurray, a playoff contender, and Daniel Suarez as he rolled up the track into the wall.
"I just lost it," Jones said. "It's unfortunate."
Before the cascading collisions ended, there were 11 cars collected in the carnage, including Matt Kenseth, who was battling with Johnson for the eighth and final playoff berth at the time.