Red Bull not to blame because Mercedes and Ferrari 'under-delivered', says Horner

Team principal Christian Horner said Red Bull's total dominance of Formula 1 this season is mainly due to the failings of their rivals Mercedes and Ferrari rather than any big steps forward from his team.

Red Bull's world champion, Max Verstappen, won his third race of the season with victory in the Miami Grand Prix on Sunday, with teammate Sergio Perez finishing second.

Red Bull have won all five races and have had four 1-2 finishes so far this season, leading some to worry the sport is becoming too predictable.

But while this is Red Bull's best-ever start to an F1 season, Horner doesn't want to take too much credit for his team.

"We feel that we've made a good step from the (previous car) but the kind of step that you would expect. It's more that it feels like others have lost ground," Horner told reporters.

No competition

The Englishman said that he has been surprised by the lack of competitiveness of the rivals.

"I think it surprised us that the others have perhaps under-delivered compared to where they were last year, but no doubt they will be looking to address that, and I'm sure, starting in Imola, we're going to see big updates starting to come through," he said.

Horner said those updates for the next race could see "big gains" for the likes of Ferrari and Mercedes, but he was clearly keen to put some pressure on them, taking aim again in his post-race interview with broadcasters Sky Sports.

READ: Red Bull's Max Verstappen after powering from 9th position to win Miami GP: 'Very satisfying'

"We are wondering: 'Where are the others?' We have made a normal step over the winter. Where did Ferrari and Mercedes go?" he asked.

Horner said the FIA sanctions against Red Bull for breaching the cost-cap, which limited their