Larson took both stage victories and led a race-high 269 of 325 laps but a 56-lap run on the same set of tyres took them beyond their limits, opening the door to the rapidly chasing Blaney.
With eight laps remaining and as Larson and Blaney both approached the lapped car of Joey Logano, Blaney dove to the inside in Turns 3 and 4 and then pulled up and in front of Larson for the lead.
Blaney’s advantage only grew after that and he eventually held off Larson for his first NASCAR Cup victory of the 2021 season.
Larson had previously taken the lead away from Blaney on lap 237 as the Penske driver took advantage of a caution – caused by Chase Elliott’s blown engine at the start of the final stage – to leap ahead of Larson out of the pitlane as the field came in to stop.
With 25 laps to go, Larson’s lead over Blaney remained stable at about 2.3 seconds, but with his tyres beginning to run out of life, Blaney was brought into play.
The Penske driver then charged up to the back of Larson’s Hendrick-run Chevrolet, taking the lead and then crossed the line with a two-second lead to secure his first ever Atlanta victory – and his fifth in his Cup Series career.
Race winner Ryan Blaney, Team Penske, Ford Mustang BodyArmor
Photo by: John Harrelson / NKP / Motorsport Images
Larson kept second place, having dominated both the first and second stages – Blaney nine seconds behind the #5 car at the second green-and-white flag, while Kyle Busch was on the receiving end of Larson’s pace after the first stage.
Alex Bowman made it two Hendrick cars in the top three, having started 14th but factoring among the front-runners all race long – running in second towards the end of the second stage before being cleared by Blaney.
Poleman Denny Hamlin collected fourth place, and had led the opening part of the race before a competition caution – called for teams to check tyre wear – tempted the lead runners to pit, which shuffled the Joe Gibbs Racing driver behind Larson.
Hamlin’s JGR Toyota stablemate Busch was fifth after finishing second in the first stage, after being forced to recover from a penalty after speeding in the pitlane and being dropped to the back of the field.
Richard Childress Racing’s Austin Dillon was sixth ahead of Chris Buescher, with William Byron eighth ahead of Martin Truex Jr and Kevin Harvick – who rallied from a flat tyre early in the race, which put him a lap down, to finish in the top-10.
Elliott had failed the pre-race inspection and was forced to start from the back having qualified fifth, but produced a strong recovery to factor within the top 10 until his engine failure put him out of the race.
Hamlin retained the lead of the current Cup Series standings, extending his advantage on points as second-placed Brad Keselowski endured a difficult race to finish 28th.