Horner says Max Verstappen making the difference as Norris challenges
Triple Formula One world champion Verstappen took his seventh win in 10 races from second on the grid with McLaren's Lando Norris on pole.
The win stretched the triple world champion's overall lead to a mighty 69 points, with Norris now his closest title challenger.
"Job one was passing Lando into turn one," Horner told reporters of how it all turned out right despite Mercedes' George Russell stealing the lead at the start.
"And then it was a race that was always going to be dominated by tyre wear. And so being quick to pass George was crucial. And he pushed hard on that first lap or two to get the pass on George.
"Today was all about not making any mistakes and Max drove a perfect race.
"Last year was a unicorn year and now is a more normal year where it's not normal to win all of the races all of the time and we're having to fight very, very hard for them. And Max is making the key difference."
Red Bull won 21 of 22 races last year, the most dominant season on record, with Verstappen triumphant in 19.
This season there have already been four different winners, including Norris in Miami, and four different pole sitters in the last four races. Red Bull have also set the fastest lap only twice.
Verstappen's Mexican team mate Sergio Perez has scored barely half the number of points as the champion and is languishing in fifth place overall.
Horner said Norris would have been hard to beat at the Circuit de Catalunya had he not messed up the start and lost track position. Verstappen was leading from lap three and then able to build a buffer.
The McLaren and Red Bull finished 2.2 seconds apart, after Norris fought back, and well clear of the rest.
"I would say that Lando has emerged from the pack as the most consistent challenger," Horner said of Norris who has now had four second places and a win from the last six rounds.
Norris said moving up to second in the championship, ahead of Ferrari's Charles Leclerc, was of secondary importance to closing the gap in performance to Verstappen.
"I think we should have done better today. We should have got some points back on Max. Potentially, there was a chance to beat him in Canada. So two races that I finished second and he's won," he said.
"Even though I moved into second in the championship, that doesn't matter," he added. "I couldn't care if I was second or 10th. It's more about the gap to what Max is and he's still extending it at the minute.
"There's a lot of, and there kind of always has been, a lot of ‘shoulda, woulda, couldas’. But we have what it takes (to win). It's just about putting it all together.