Max Verstappen had looked on for a comfortable second-place finish and another 18 points in the bag, but his car suddenly slowed with 20 laps remaining in Sunday’s 58-lap race.
His DNF was his second mechanical problem in the first three races of the season and is proving hugely costly in the Drivers’ Championship, as the reigning World Champion now trails Charles Leclerc by 46 points.
“It’s totally understandable, his frustration. That was a really, really disappointing result not to finish the race,” Horner explained to Sky Sports F1.
“Obviously, it’s very frustrating to have a DNF on Max’s car,” Horner said.
“It looks like a fuel system issue, external to the tank, that has caused the issue.
“So obviously, it’s gone into quarantine, the parts will obviously return to Japan, and we’ll obviously try and understand the problem as quickly as we can.”
A fuel supply issue would be a similar problem to what forced Verstappen out of the season opener in Bahrain.
“Obviously we need to understand those and address them quickly,” Horner said.
“In the first two races, for Max, we’ve given up 36 points and for the team, we’ve given up 50 points. When you look at that, both the constructors’ and the drivers’ championship would be a lot different.”