Following Renault's refusal to extend its engine supply efforts to a fourth team in 2018, McLaren's hopes are now tied to a hypothetical Toro Rosso-Honda deal.
Sunday could prove an all-important day for the Woking-based outfit as talks come to a head between Red Bull and Honda regarding a potential partnership between the Japanese manufacturer and Toro Rosso.
McLaren is hoping to be powered by Renault next season, thus ditching its deal with Honda after another dismal season of disappointing results.
But the French manufacturer could not be persuaded to supply a fourth outfit in addition to Red Bull Racing, Toro Rosso and its own works team.
If Toro Rosso commits to Honda however, its current supply of Renault engines could be transferred over to McLaren.
Logistical reasons are at the forefront of Renault's decision not to extend its efforts, although its current run of poor reliability was obviously also an important factor.
"It is many little different things that need to be addressed. It is the whole thing that has to improve in quality, but I have all the confidence in the management structure to do that," Cyril Abiteboul told Motorsport.com, speaking about Renault's mechanical woes.
"And frankly, that is one of the reasons why we do not want to have more customers than we already have.
"We do not want to dilute the effort that goes into next year and to the fact that next year’s engine will be designed in a very reliable manner."
Beyond McLaren's quandary, Honda has expressed its will to remain in Formula 1, but if an agreement cannot be reached with Toro Rosso, the McLaren-Honda partnership will likely have no other choice but to continue. Without Fernando Alonso?