With Red Bull's split with Renault all but confirmed, questions remain as to who would supply the former world championship team next year with only Ferrari and Mercedes available as realistic choices.
It is rumored that Mercedes top brass are reluctant to supply Dietrich Mateschitz's outfit with its engines as it would pose a direct threat to the dominance and a success of its own F1 team.
Mercedes motorsport boss Toto Wolff recently addressed the eventuality of a partnership with Red Bull, but mainly emphasized the perils of such a deal for the German manufacturer's own interests.
"If I judge it from the perspective of our team, it is an agreement that you should not do," said Wolff. "Our car and our successes are the result of hard work and huge investment from Daimler."
"We built our supremacy, while today there is a team that has decided that they do not want to stay with their partners. It is a different philosophy to ours."
According to Motorsport.com, it is now understood that Dieter Zetsche, the chairman of parent company Daimler, is now adverse to the idea of partnering with Red Bull following talks over the weekend at Monza with team representatives Toto Wolff and Niki Lauda.
If true, this leaves only Ferrari as the single source of engine power available for Red Bull next year. It's widely speculated that Toro Rosso will be added to Ferrari's pool of clients for 2016, in addition to Sauber, Manor and Haas.
Red Bull would therefore become a fifth entity which Ferrari would supply, raising questions about its potential resource capacity should a supply deal become effective.