Red Bull's team principal, Christian Horner, has attributed the current season's utter supremacy of his team in Formula One to the shortcomings of their competitors, Mercedes and Ferrari, rather than any significant strides made by his own 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 had four 1-2 finishes 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.

The Englishman said that he had 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'll see big updates starting to come through," he said.

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

"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 testing ability, meant their updates would likely come online later in the season.

But despite Verstappen and Perez being in a league of their own so far this season and Red Bull already 122 points clear in the constructor's championship, Horner said much remained to be fought for.

"We've got a great car, we've got a great team, we've got two great drivers, but still a long way to go," he said. "Let's reserve judgment until after we see what it turns out to be at Imola (Monaco) and Barcelona."

Dimming expectations

Struggling Mercedes enjoyed better-than-expected results at Miami, with George Russell finishing fourth and Lewis Hamilton sixth, but the team was quick to dampen expectations about upgrades, expected to be delivered in time for the Emilia Romagna Grand Prix at Imola on May 21.

"There are a lot of expectations on Imola, but at the end of the day, we finished 30-odd seconds behind the leaders today," said Russell.

"I am sure it is going to take a step in the right direction, but it will not transform things. Let's hope it does.

"The car is a little unpredictable at the moment, so hopefully, it exceeds our expectations in the next race, but it will be a long journey."