Renault advisor Alain Prost says a question mark about Sebastian Vettel's motivation may have thwarted his chances of joining the French team.
The Enstone based team decided instead to sign up Fernando Alonso for 2021, with German Vettel admitting he had talks.
"They made a different choice, but that doesn't change my plans," the 33-year-old insists.
Prost admits Renault also considered Valtteri Bottas.
"There were the three great champions (under consideration): Fernando Alonso, Sebastian Vettel and Valtteri Bottas," the F1 legend told RMC Sport.
"It was a little less obvious for Sebastian in the sense that his motivation was not very clear," he said.
"It was also difficult for Valtteri in that he has the best car. We wanted someone who is not a replacement option, but someone who is fully motivated for the project."
Prost also admits that Renault's marketing arm is happy with the team's former two-time champion Alonso as the eventual choice.
"Making a choice only for marketing would be a mistake," he said, "but all the manufacturers in F1 want to reduce costs.
"It is normal that there is a marketing aspect, but that is not the main reason."
Indeed, Alonso is one of the greatest ever drivers in Formula 1 - but many wonder whether his notoriously difficult character will re-emerge at Renault.
"This is a subject that I raised with him," Prost admits. "Frankly, this is the risky side, but he talks about it openly.
"He says that he has changed a lot and that his sabbatical years have matured him. In a way, he knows that he has no right to disappoint on this level."
Alonso will replace the McLaren-bound Daniel Ricciardo, but the Australian driver said he will not make it easy for the incoming Spaniard by offering his car in Friday practice sessions this year.
"I heard the words 'help Fernando Alonso'. He doesn't need any help," said Ricciardo.
Team boss Cyril Abiteboul says another option for Alonso might be tests in the two-year-old Renault that the team recently prepared for the pre-Austria GP preparations.
"We still have that option," said the Frenchman, "but that is not confirmed. We don't have a firm plan on that."
