A fairly routine Japanese Grand Prix was punctuated by one chaotic moment as Lando Norris and Max Verstappen raced out of the pit lane during their stop, the former running into the grass in an effort to emerge on track ahead.

A slow stop for Verstappen enabled the rivals to run close together at the pit exit, and according to Red Bull team boss Christian Horner, that was the result of a reserve pit crew working in Japan this weekend.

Max Verstappen’s slow stop led to the moment of the race

A fairly processional Japanese Grand Prix saw only a handful of spicy moments to keep things exciting, and perhaps there was no bigger moment than the pit exit run-in between Max Verstappen and Lando Norris.

Both drivers had remained in qualifying order through the first stint of the race at Suzuka, and the two pitted at exactly the same time for a swap to fresh rubber.

Though Verstappen entered the pits with a lead of over a second on Norris, the two drivers found themselves vying for space at the exit. Already in the fast lane, the reigning had staked his claim on his pit exit position when Norris tried to dart into the same bit of track space.

Verstappen held firm, and Norris ultimately went running through the grass on the right-hand side of the pit exit.

Not long after, the Briton radioed into his McLaren team to allege that Verstappen “forced me off.” The event, however, went unpunished by the stewards, and the reigning champion went on to win the race.

More Japanese GP analysis:

👉 McLaren’s strategy indecision is the biggest threat to their title chances

👉 Max Verstappen the GOAT? Surprise Japanese GP pole hints at Senna-esque title tilt

But what went wrong with Verstappen’s pit stop? Where did his gap to Norris go?

The Dutch driver held about a second lead over Norris when the two peeled into the pits for new rubber — and that gap was almost entirely neutralized by a slower stop for Verstappen.

The Red Bull crew clocked a 3.3-second stop to McLaren’s 2.3-second stop, which meant both drivers arrived at the pit exit at the same time. Red Bull’s stop was uncharacteristically slow, particularly at such a decisive moment in the Grand Prix.

But Christian Horner has an explanation.

Speaking to media after the Japanese Grand Prix, the Red Bull team principal admitted that “we didn’t have a totally clean pit stop.

“We’ve got a reserve crew with two members missing this weekend, and Lando got close-ish at the pit exit but he never looked alongside or anything like that.”

He offered even more clarity to F1TV, saying, “The two number one mechanics, who are twins, on the car, unfortunately, their dad has not been well, so they’ve gone back to the UK.

“So, we got the reserve guys on the pit stop, and we had a slightly slower stop than would have been ideal.”

Most Formula 1 teams have a standard pit crew as well as several reserve crew members who can pop in as necessary. The reserve crew has become especially important in the modern era, as more and more races appear on the calendar. Crew members needing a physical, mental, or personal break are able to take that time thanks to reserve crews.

Read next: Explained: Why McLaren opted against strategic gambles in Japanese GP defeat