Red Bull 'can be invincible' but competitors are catching up
He tempered it with the usual 'taking one race at a time' talk but with the team winning all eight races so far this season, and nine in a row when last year's Abu Dhabi finale is included, there was no point pretending otherwise.
"Can we? Yes. Will we? Who knows, because there are so many variables in this game," Horner told Sky Sports television after Max Verstappen took his 41st career win, equalling Ayrton Senna's tally, and the team's milestone 100th.
The question, often asked when a team starts with a winning sequence, is becoming a genuinely serious one now that the numbers are stacking up.
No team has won every race of a season since 1952, McLaren coming closest in 1988 when Alain Prost and Senna won all but one of 16 rounds. Mercedes won 19 of 21 in 2016 and there are 22 this year.
Verstappen has won six of the eight and the last four in a row and is heading for another record-breaking season but there are glimmers of hope for his rivals.
The winning margin at Montreal's Circuit Gilles Villeneuve was the smallest so far, not including Australia which effectively ended behind the safety car.
Verstappen finished 9.5 seconds clear of Aston Martin's Fernando Alonso, compared to the 24 seconds over runner-up Lewis Hamilton in Spain or the 27.9 seconds over Alonso in Monaco.
The true extent of the gap may have been distorted by Verstappen controlling the race from pole position - although he said he had to push hard to get heat in the tyres - and having a dead bird wedged behind a front brake duct.
Even so, Horner feels the competition is catching up.
"On this venue yes, the gap is shorter... it's inevitable that they are closing, we'd be surprised if that wouldn't be the case," said Horner.
Alonso was also being told by his team to 'lift and coast' to save fuel, a false alarm it later turned out, so could ultimately have gone quicker.
Aston Martin brought a major upgrade and Mercedes and Ferrari have also been working hard to bring performance to their cars.
"I think we are slowly chipping away. I think the Astons took a little bit of a step ahead this weekend when they added the upgrades but we're working on bringing some more moving forwards," said Mercedes' Hamilton.
"Max was a little bit gone but I think our pace is a little bit closer today, so we are going in the right direction."
If there is an Achilles' Heel in Red Bull's dominance, it is the current dependence on Verstappen for the top step of the podium.
Mexican team-mate Sergio Perez is now 69 points adrift, albeit still second, and has not qualified in the top 10 or stood on the podium in the last three races after a strong start to the campaign.
Alonso is now only nine points behind Perez, who was sixth in Montreal, and, asked whether he felt he could beat him in the championship, replied simply: "Yes".
Should Verstappen suffer a setback, mechanical or otherwise, the chances of the second Red Bull coming through for the win are looking a lot less certain and rivals are sensing opportunities.
Verstappen's last race retirement was in Australia in April 2022 and the last time he was beaten by someone not in a Red Bull was last November, when Mercedes's George Russell won in Brazil.
