Minardi said he has also heard that Renault is looking beyond the walls of its Viry factory and "shopping" for technical fixes.
"This news can only feed suspicions of structural problems in the engine that are not easy to solve in the short term," he said.
However, addressing publications on Friday, Renault's engineering chief Remi Taffin said the speculation about the French marque's problems is overblown.
"The problems are worse from the outside than they are from the inside," he said.
"It's a difficult moment but we will get through this."
It was believed Renault had come some way in fixing the problems struck at Jerez, when Lotus debuted its new E22 without trouble just a week ago.
But it subsequently emerged that a 'filming' day at Misano for the similarly Renault-powered Toro Rosso did not go so well.
Taffin said the Toro Rosso issues were "not a surprise -- we knew what we had in the car and we thought we would get away with it, but obviously not".
The Frenchman said the major problem at Jerez was hardware and software, and that he is confident Renault will arrive for next week's testing in Bahrain "without all these issues".
Still, there is no guarantee, as he said Renault is still working on the software problems.
"We are trying do everything at the same time, but then sometimes we have to prioritise so it's not easy to have everything altogether at once," said Taffin.
While admitting Renault is obviously behind schedule, he denied it will take "months" to catch up, insisting all the actual parts of the power unit are sound.
"We are at least where we would have sought to be for the first test, so maybe now we are three weeks behind, and now we are on a recovery plan," said Taffin.
In the meantime, world champion Sebastian Vettel on Friday seemed to acknowledge that amid Renault's problems, F1's Mercedes-powered cars appear to have the upper hand for now.
"All the Mercedes powered cars looked very strong at Jerez," the German told Sport Bild magazine.
"But that is no surprise, as we have known for some time how much time and effort Mercedes has invested in the new power train," added Vettel.