Larson first noticed an electrical problem on his car early in Stage 2 and when he pit under caution on Lap 34, his team discovered he had lost an alternator belt.
Changing the battery provided a quick fix but the team formulated a plan to change the belt under additional stops. Once the work was complete, Larson’s car was as fast as ever.
He got inside leader Denny Hamlin off Turn 4 on a restart on Lap 102 and moved into the lead for the first time in the race. Larson led the final eight laps and held off Tyler Reddick by .782 seconds to win the Bank of America Roval 400.
The win is Larson’s seventh of the 2021 season, the most of any driver. And he sits with a big points advantage heading into the semifinal round of the NASCAR Cup Series playoffs, which open next Sunday at Texas Motor Speedway.
“I did not see us winning,” Larson said following an enormous burnout on the frontstretch of the track. I didn’t really feel that good early. We started to change some things and the team did a good job of letting me know what to do inside the cockpit to do better.
“Around that time, I noticed my battery was getting low and I was like, ‘Man, I’m not going to get knocked out of the playoffs like this?’ It wasn’t looking too good. Thankfully, everybody on our No. 5 car did a good job of staying calm.
“Cliff (Daniels, crew chief) did a great job of communicating with me on what was going on like getting the battery changed and whatever else it took. William was also good and it was a bummer not to see it work out for him.
“This is an awesome day for Hendrick Motorsports.”
Joining Larson in the semifinal round are Denny Hamlin, Joey Logano, Ryan Blaney, Kyle Busch, Chase Elliott, Brad Keselowski and Martin Truex Jr.
Eliminated from further title contention after the race were Kevin Harvick, Alex Bowman, William Byron and Christopher Bell.
Chris Buescher finished third in the race, Kyle Busch was fourth and Hamlin rounded out the top-five.
Following the break between Stages 2 and 3, several lead-lap cars pit with Kyle Busch the first off pit road among those who did.
Byron led the way on the restart on Lap 54 followed by Austin Dillon and Hamlin.
On Lap 55, Harvick got into Elliott, who slammed into the wall and also made contact with Cole Custer. Elliott’s No. 9 required extensive repairs but he managed to remain on the lead lap.
The race returned to green on Lap 58 with Byron still out front, followed by Austin Dillon and Hamlin.
On Lap 59, A.J. Allmendinger had to take his No. 16 Chevrolet to the garage with an apparent engine issue.
Hamlin missed the backstretch chicane on Lap 70 and was forced to serve a stop-and-go penalty on the frontstretch. He dropped from third to sixth in the running order.
Larson, Bell and Michael McDowell were among the first cars to make a green-flag pit stop on Lap 74.
Kyle Busch, Truex, Harvick and Logano all pit on Lap 75. Byron and Reddick both pit on Lap 76, which turned the lead over to Kurt Busch.
Once the cycle of stops was completed on Lap 81, Byron returned to the lead. He was followed by Reddick, Austin Dillon and Kurt Busch.
With 24 laps to go, a piece of Elliott’s rear bumper cover was dangling behind the car. It finally fell off and onto the track and prompted NASCAR to throw a caution on Lap 87.
Most of the lead-lap cars pit under the caution with Kurt Busch the first off pit road. Hamlin elected to stay out and led the way when the race resumed on Lap 90.
On Lap 91, Byron missed the backstretch chicane after contact with Reddick and was forced to serve a stop-and-go penalty, which dropped him to 12th in the running order.
Corey LaJoie slammed the Turn 2 wall on Lap 93, which left debris across the track, and brought out the eighth caution of the race. Joey Hand was also caught up in the incident.
Several drivers pit but Hamlin remained in the lead when the race returned to green on Lap 96.
Entering Turn 1 on Lap 99, Harvick locked up his brakes, failed to make the turn and hit the wall hard, bringing an end to his race and playoff run.
The race returned to green on Lap 102 with Hamlin still out front. He was followed by Larson, Reddick, Buescher and Logano.
Larson got inside of Hamlin off Turn 4 on the restart and moved into the lead for the first time in the race. Reddick moved to second and Byron into third.
Kyle Busch cruised to the Stage 2 victory over Elliott while several playoff drivers encountered problems.
Harvick was third, Blaney fourth and Logano rounded out the top-five.
Following the break between Stages 1 and 2, several lead-lap cars elected to pit and Elliott was the first off pit road among that group.
Allmendinger remained on the track and in the lead when the race returned to green on Lap 30. He was followed by Kyle Busch and Byron.
On fresh tires, Kyle Busch quickly moved into the lead off Turn 4 and Byron moved into second behind him as Allmendinger dropped to third.
Chase Briscoe spun out on the frontstretch following contact from Ricky Stenhouse Jr. on Lap 34 to bring out the fourth caution of the race.
Several lead-lap cars pit, including Larson and Bowman, who both had developed electrical issues. Both made extended stops on pit road but their problems persisted and likely would require a change of batteries.
The race resumed on Lap 36 with Kyle Busch still out front.
With 10 laps remaining in the stage, Kyle Busch held about a 1-second lead over Harvick as Byron ran third.
With five laps to go, Kyle Busch led Harvick by 1.3 seconds as Elliott moved up to third.
With two laps to go, many of the lead-lap car elected to pit for new tires but Kyle Busch remained in the lead.
Elliott out-braked Allmendinger entering the backstretch chicane on the final lap to grab the lead and held on for the Stage 1 win.
Blaney was third, Truex fourth and Logano rounded out the top-five.
Hamlin started on the pole and grabbed a big lead until several teams elected to pit under green for new tires prior to the competition caution.
Hamlin was among those who pit, turning the lead over to Logano on Lap 10. Bell was penalized for speeding on pit road during his stop and had to serve a pass-thru penalty on pit road.
The competition caution was displayed on Lap 12. Several other drivers pit during the caution for new tires and fuel but Logano remained on the track and in the lead when the race returned to green on Lap 14.
Blaney powered to the lead shortly after the restart while Keselowski spun near the backstretch chicane but was able to continue on without a caution.
With seven laps remaining in the stage, Elliott moved into second behind Blaney as Logano dropped to third.
On Lap 20, Ryan Newman hit the wall off Turn 14 to bring out the caution and nearly missed hitting Keselowski.
Several lead-lap cars pit and Hamlin was first off pit road among those who did. However, he was penalized for speeding on pit road and had to restart from the rear of the field.
The race resumed on Lap 23 with Blaney still out front, followed by Elliott and Logano.
Allmendinger got around Blaney off Turn 2 on the restart to grab the lead for the first time in the race.