The fallout between Red Bull and their engine supplier Renault is continuing and is putting the former champions in a particularly awkward dilemma.
The two have been trading barbs since the opening race of the season in Australia, as Red Bull put the blame for their poor performance at Albert Park squarely at their partner's door.
Both Daniel Ricciardo and Daniil Kvyat complained all weekend about the V6 power unit being virtually undrivable in Melbourne as well as been approximately 100 brake horsepower down on their rivals Mercedes and Ferrari.
Red Bull chassis as much to blame - Renault
The reliability wasn't much better as Ricciardo had to switch to a second of four allocated engines for this year and Kvyat failed to make the start as an oil pressure issue prevented him from making the start.
The French manufacturer has since gone on an aggressive development programme and claims that progress has been made as they refine the software learning from the data collected at the first race.
Blame game in full swing
Despite that, however, Renault is refusing to take full responsibility for Red Bull's problems after being quoted by Crash.net as saying some of the huge deficit to their rivals on track are as much chassis as they are engine based.
“It's therefore the overall package that needs some help and we have been working with the team to move forward,” Cyril Abiteboul the head of Renault Sport added.
“We've been particularly aggressive in development and we should see the results a lot more clearly in Malaysia, particularly since we have had the opportunity to refine the power unit using the data from Australia.
“Work is still ongoing but even now we are in a completely different place to where we finished Melbourne.”
Later, however, Abiteboul would be more scathing in his comments towards Red Bull and focussed his attack on designer Adrian Newey.
“It's hard to have a partner who lies,” Abiteboul told French publication Auto Hebdo. “Adrian [Newey] is a charming gentleman and an outstanding engineer, but he spent his life in criticising his engine suppliers. He's too old to change.”
Toro Rosso progress backing up claim
Backing up Renault's claims, however, it does seem clear that the issues facing Red Bull are more extreme than those seen at Toro Rosso.
The junior team was close to the top of the mileage charts in pre-season testing and enjoyed some success at the opening race with Carlos Sainz scoring points albeit with team-mate Max Verstappen retiring.
Much of their progress is down to a different design philosophy between the two Red Bull-backed teams. With Newey, Red Bull have always been very extreme cars aerodynamically without much care for the mechanical parts inside and that has sometimes led to greater unreliability, whereas Toro Rosso follow in Williams direction and produce a very slippery car that can achieve much higher speeds than its bigger brother but not match it in the corners.
Because of the less extreme packaging at the rear of the Toro Rosso it also allows for great cooling and therefore, usually, better reliability.
Did Renault cause Red Bull fall?
On Red Bull's part their argument hasn't just been about how poor the Renault power unit was but how uneven the four power units in F1 currently are.
Team boss Christian Horner even suggested efforts should be made the equalise the engine performance but his comments were largely met with a negative response.
Most see them as mere sour grapes that the team have fallen so far from the heights they were at the end of 2013 but in two ways Red Bull's downfall is Renault's fault.
It was the French carmaker who led the calls for the more fuel efficient engine formula, which resulted in the V6 turbo hybrids of today, and then in the developmental race of the new power units, that they called for, they fell behind the big money spenders at Ferrari and particularly Mercedes, also, given Honda's investment it may be that they too will overtake Renault in the months ahead.
Red Bull, Renault heading for divorce?
Interestingly, the recent drop in relations between team and supplier comes as speculation suggests Renault are considering a full return to F1 as a works team and to do so they could purchase Red Bull's junior outfit.
Should that be the case it would likely see Red Bull look elsewhere for their power units. As there is a belief that a working partnership is now more beneficial than simply being a customer, it is being suggested that they could entice another car maker back into the sport with Volkswagen or build their own engines in-house.
Certainly any deal with any of the other three suppliers currently in F1 would seem very unlikely indeed so, going forward, its a case of either getting down to work and making the improvement to close the gap with Renault or start making plans for life after their long-time supplier, a road that could take several more years to return to the top. A very tricky decision indeed for the former world champions.