Who is Justin Allgaier? Meet Kyle Larson's backup driver, who is replacing NASCAR points leader at Coca-Cola 600

Only five drivers in auto racing history have achieved "The Double" — a feat that involves competing in both IndyCar's Indianapolis 500 and NASCAR's Coca-Cola 600 on the same day.

Kyle Larson sought to become the sixth in 2024. He won't be able to complete both races in full because of reasons beyond his control.

Rain and lightning near the Indianapolis Motor Speedway delayed the start of the Indy 500 by several hours. Larson would have needed to leave the race by 4 p.m. ET to make it to the Coca-Cola 600, so he had to choose the race in which he wanted to officially participate.

Ultimately, Larson stayed put to compete at the Indy 500. That allowed his backup driver — Justin Allgaier — to draw into the Coca-Cola 600. While Larson might eventually arrive at the Coca-Cola 600 and replace Allgaier, all credit for the race will go to the veteran NASCAR driver.

Here's what to know about Allgaier as he replaces NASCAR's points leader on one of the racing circuit's biggest stages.

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Who is Justin Allgaier?

Allgaier is a veteran driver who has run more than 500 combined races at the NASCAR races in his career. A bulk of his 15-year NASCAR career has been spent on the Xfinity Series, where he has run 449 with 24 wins and 267 top-10 finishes, but he's been called up to the Cup Series level 81 times.

Allgaier has just one top-10 finish at the NASCAR Cup Series level in 87 races. The 37-year-old hasn't won at that level either, as his best-ever finish was an eighth-place mark at the 2015 Food City 500.

Allgaier hasn't run a race with the NASCAR Cup Series since the 2022 YellaWood 500 at Talladega. He finished 30th in that race. He will look to improve upon that as he returns to the series for the first time since October of 2022.

What happened to Kyle Larson?

Larson was forced to choose between the Indy 500 and Coca-Cola 600 after the former race was delayed by rain in Indianapolis.

Larson explained to the NBC broadcast that he always planned to prioritize the Indy 500.

"I think our plan is to keep this as the priority," Larson said. "I would be here racing."

The NASCAR points leader went on to say that he was "kinda bummed" about the rain. He wanted it to either wash the race out completely or never arrive at all.

Instead, the "worst-case scenario" occurred for him. His attempt to run the double would have required him to leave Indianapolis at around 4 p.m. ET, or shortly thereafter, to make it to Charlotte for his second race. The Indy 500 is tentatively scheduled to begin at 4:44 p.m. ET after a four-hour delay.

Still, he found a silver lining in his failed attempt to make auto racing history.

"We'll get to get on track at least in something today, so that's exciting," Larson said.

And Allgaier will be thankful to Larson for giving him a chance to run in the Coca-Cola 600, something that few backup drivers behind "Double Duty" participants have done.

Backup drivers at the Coca-Cola 600

A backup driver has only run in place of a competitor looking to complete "The Double" once since John Andretti first attempted the feat in 1994. That came in 2000, when P.J. Jones started the Coca-Cola 600 ahead of Robby Gordon after rain delayed the Indy 500 by three hours.

Gordon eventually replaced Jones midway through the Coca-Cola 600 and finished the race. However, Jones was credited for all laps completed because he started the race.

Allgaier is in a similar spot to Jones, as Larson's run in the 2024 Indy 500 is set to be delayed by about four hours. Larson is still planning to finish the Coca-Cola 600, according to NBC's Indy 500 broadcast, but it remains to be seen how many laps he will complete after he arrives in Charlotte.

Below is a look at "The Double" participants and their backup drivers over the years:

Jones was the only backup driver to actually race in the Coca-Cola 600, so Allgaier's opportunity will be a rare one.