Red Bull is hopeful it can claw back some of the deficit to Ferrari and Mercedes without a major 2017 engine upgrade from power unit supplier Renault.
Renault recently dismissed speculation about a possible engine upgrade for the upcoming Azerbaiajan Grand Prix, stating it is expecting small improvements in Baku instead of a wholescale change to the power unit. The news is a blow to Red Bull after a slow start to the season, which has seen it linger a distant third behind the developing title fight between Ferrari and world champions Mercedes.
But Red Bull hopes there is performance gain to be found elsewhere, namely from fuel and lubricants supplier ExxonMobil, which joined the team after ending its long-standing partnership with McLaren in 2016.
"This is Renault's decision," Horner told F1.com about Renault's decision not to bring a major upgrade this season. "We take whatever we can, when we can -- for sure we'd rather sooner than later! We knew that Montreal would be tricky and so will be the next two races, Azerbaijan and Austria. We will probably introduce our next engine [from the season's allotted allocation] in Austria -- and hopefully that will be a bit of a boost as our fuel supplier ExxonMobil did a great job finding performance. In this area there is quite a bit of potential."
ExxonMobil's fuel and lubricants are a point of difference for Red Bull as Renault's factory team uses BP fuel and Castrol lubricants for the same engine -- one Red Bull runs under the TAG-Heuer branding. Fuel and lubricants are a key but understated part of modern F1 engines, with Mercedes' link up with Petronas leading to undoubted performance benefits since the start of the turbo-hybrid era.
Even though Renault's factory team works with a different fuel and oil supplier, ExxonMobil insists this does not put Red Bull at a disadvantage.
"From the Renault side of it I think they view it as good competition for the lubricants and fuels," David Tsurusaki, ExxonMobil's global motorsports technology manager, told ESPN in Montreal. "We view it, our team views it as a competition - we want to win, we want to be better. I have told my team as recently as last week that timing-wise will continue to send and develop products and when we get a chance to test and get it approved it will my challenge to work with the engine manufacturers.
"But we're not going to hold back, we're not going to wait. We're going to say 'OK, we have five new fuels, five new lubricants we want tested and evaluated, tell us when you can do it'. So that part of it is probably a little bit of a challenge but it's working. We're getting things done and the Renault guys are working with us pretty strongly, they've got someone assigned to us so communications are good. It's working."
Red Bull has refused to lay the blame for its slow start to 2017 solely at Renault's feet, as it did in 2015, and Tsurusaki says the late confirmation of the ExxonMobil deal last year has undoubtedly hurt the team's performance in the opening races of this campaign.
When it was put to him that F1 can judge new partnerships in terms of immediate results, Tsurusaki said: "Exactly, and that was a problem. If you start normal in planning, you start planning for the next year the previous year. We didn't have that opportunity, as a matter of fact there was a lot of challenges for the technical group because we were saying 'we need to start thinking about 2017'.
"So that timeline was the challenge so if you're starting January 1 and you think you've got testing and races coming up, jump on it guys. But our fuels and lubricants guys took on the challenge and said 'we can do that', as long as we get the test time and opportunity to look at the products. I can tell you the first product which went in didn't work but we figured it out pretty quickly."