Blaney won when the caution came out coming to the checkered flag in overtime, ending the race five laps beyond the scheduled distance.
The caution waved after Daniel Suarez was turned into Kevin Harvick, triggering a multi-car crash. Austin Dillon was among those collected, ending his last-gasp bid to beat Reddick, his teammate at Richard Childress Racing, for the final playoff spot.
“Playoffs, here we come,” Reddick said on his team’s radio.
Blaney’s victory was his third this season. He also won last week at Michigan.
“You never know how the end of these are going to play out,” Blaney told NBC Sports’ Marty Snider. “Winning at Daytona is so cool. … Man, it’s been a fun two weeks.”
Chris Buescher crossed the finish line second but his car was disqualified after failing post-race inspection. His car’s track bar assembly did not conform to the rules.
Kyle Larson placed 20th and won the regular-season title.
“Our team worked so hard the regular season,” Larson told NBC Sports.
Blaney will enter the playoffs as the No. 2 seed.
Overtime was set up when the caution came out four laps from the scheduled end when Chase Elliott, who was leading and was hit by Matt DiBenedetto after contact from behind. The crash collected Brad Keselowski and Kyle Busch, among others.
The intensity increased in the final 20 laps. Martin Truex Jr. was turned 14 laps from the scheduled end as cars stacked up in front of him. The contact sent him into William Byron and back down the track. Truex’s car then was hit by Tyler Reddick, who entered the race holding the final playoff spot. Reddick’s car began smoking, but the team told him to continue after checking the damage on pit road. Reddick told his team that his oil pressure, water pressure and fuel pressure was fine.
The race was stopped for the 10-car crash with 13 laps from the scheduled end.
STAGE 1 WINNER: Chase Elliott
STAGE 2 WINNER: Joey Logano
WHO HAD A GOOD RACE: Bubba Wallace placed a season-best second. … Justin Haley finished a season-high sixth a few hours after he won the Xfinity race at Daytona. … BJ McLeod placed a career-best ninth. His previous best finish was 19th in the 2019 Daytona 500. … Josh Bilicki finished a career-high 10th. His previous best finish was 18th at the Indianapolis road course earlier this month.
WHO HAD A BAD RACE: Daytona 500 winner Michael McDowell finished 39th in the 40-car field after blowing an engine early. That came after issues in inspection before the race that led to NASCAR ejecting McDowell’s crew chief, Drew Blickensderfer.
NOTABLE: NASCAR announced that Chris Buescher’s car was disqualified after finishing second. The car’s track bar assembly did not conform to regulations. The issue was discovered in inspection after the race.
NEXT: The playoffs open Sept. 5 with the Southern 500 (6 p.m. ET on NBCSN)