Christian Horner maintains Red Bull Racing has done the right thing by ditching its engine supply from Renault, even though the lack of an immediate replacement puts its participation in Formula 1 in doubt.
Despite enjoying substantial success together during the 2.4-litre V8 era, which yielded four consecutive world titles between 2010 and 2013, Renault's failure to get a competitive and reliable grasp on the V6 Hybrid power units has prompted scathing criticism from top brass across Red Bull.
With the spat becoming increasingly public, the rift between the two parties reached an irreparable stage earlier this season and has subsequently resulted in the annulling of its contract together a year early.
While Renault has opted to go it alone by reforming its own manufacturer effort with the buy-out of Lotus, Red Bull – and also Toro Rosso - remain without engine supplies for 2016.
However, with a rejection from Mercedes leaving Ferrari as the only obvious candidate for Red Bull, Horner insists the limited options are not a reason to have retained Renault, saying the French firm is two or three years behind in development.
"Since the power unit regulation change, it's a very different world that we're living in," Horner told Sky Sports F1. "There's really only two engines out there that you can compete for grand prix victories with and, unfortunately, Renault have fallen behind that.
“It looks like it's going to be at least two to three years before they can be in a position to compete again. As a paying customer, we can't afford to wait that long."
Though Ferrari has suggested it is willing to supply engines to Red Bull and Toro Rosso – in spite of also taking on the incoming Haas F1 team for 2016 -, it is less keen to provide the factory-level parity that Red Bull is demanding. Indeed, Ferrari's first engine offer is said to have been akin to that given to Sauber.
However, while many have asked why any manufacturer would want to supply Red Bull given its outspoken attitude towards Renault, Horner doesn't believe it will deter future partners.
"Perhaps we have been guilty of being honest, whether that is my comments or Adrian Newey's comments or Helmut Marko's or most important of all Dietrich Mateschitz's as he is paying the bill at the end of the day. I don't believe that would have an impact on influencing any other supplier."