It is no secret that this week's F1 pre-season test at Bahrain International Circuit could be key to Red Bull Racing's chances of retaining its world titles, but could also have significance for its long-term relationship with engine partner Renault.

That is the claim of former F1 team owner Giancarlo Minardi, who suggests that ongoing reliability problems for the French engine supplier could prompt the four-time reigning champions to explore alternatives for 2015.

While it is locked in with Renault for the coming year, Red Bull completed only 21 laps in the four days of running at Jerez last month and, along with the regie's other customers - Toro Rosso and Caterham - lags behind the various Ferrari and Mercedes runners in terms of track time with just eight days of preparation left before the opening round of the 2014 campaign in Australia.

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While Lotus claims to have completed 100km of trouble-free running with the private debut of its E22 in Spain last week, Toro Rosso apparently could not claim similar results from its own 'filming day', and the four Renault-powered teams will head to BIC with doubts remaining over their potential.

While the French giant admits that there is still work to be done on its turbocharged V6 'power unit', it claims that it is not 'months behind schedule', as had been suggested, but Minardi still felt compelled to claim that Red Bull might consider moving on next season. Alternator problems with Renault's previous V8 unit caused rare retirements for Sebastian Vettel in 2012 and should it not find itself able to race with the likes of Ferrari and Mercedes this season, Minardi recycled rumours that the world champions could be 'thinking about changing their engine supplier in 2015'.

"One month ahead of the Australian GP and after the first pre-season test at Jerez, we're witnessing many changes of technicians and teams, who, concerned about the engine issues occurred during the first session, are taking their first measures for the 2015 season," the Italian wrote on his website, "These changes are very similar to the ones occurring in football, where, during the pre-season phase, it can happen that some football coaches are relieved and some teams have to resort to the football market to replace some vacancies.

"Despite Renault, Red Bull and Toro Rosso putting a lot of effort into injecting calm and tranquillity to the audience by issuing comforting press releases and giving reassuring interviews, the situation seems to be more complicated than expected and it's not easy to solve it. It is rumoured that Red Bull are and Toro Rosso changed their technical director for the sixth/seventh time in their history.

"As far as engine is concerned, according to some information coming from abroad, Renault is trying to hire technicians beyond the transalpine borders (without success). This has never happened before, as the French company has always tried to protect its technology. News like that fuel some doubts about possible engine structural issues, which seem to be not so easy to solve over the short term.

Some manufacturers, who are currently not engaged in the F1 Championship, have a personal unit already made and are taking into account the possibility to join the top series, even if they're having some troubles finding an important partner to go into partnership with, unless they are capable to exploit Renault's current failure.

Obviously I hope to be belied in few weeks, during the second pre-season test session in Bahrain, where teams and engine manufactures will bring their technical amendments, [but] this is a very messy moment for F1."

The Red Bull rumours, however, do not appear to take into account the team's lucrative tie-up with title sponsor Infiniti, which is part of the larger automotive alliance between Renault and Nissan.

Meanwhile, Toro Rosso, which was Minardi's team before being bought by Red Bull, is also rumoured to have parted company with chief designer Luca Furbatto.