Aulas made it clear no deal has been done to take Ndombele away from Lyon and indicated a preference to keep him, though he acknowledged "the biggest European clubs" are pursuing the midfielder.
Tuesday's arrival of Brazilian youngster Jean Lucas from Flamengo stoked speculation surrounding Ndombele, with Tottenham and Paris Saint-Germain understood to be among those keen on signing the 22-year-old.
During Jean Lucas' presentation news conference, Aulas provided an update on Ndombele's future and even highlighted Lille's Thiago Mendes as a potential replacement for the midfielder who has emerged as one of Ligue 1's top players during his two seasons at Lyon.
"We would need substantial proposals so that we can move forward with Tanguy [his plans], who is eventually interested in leaving," said Aulas.
"But if he were to leave, which is not the case today, we would have to make signings, which is what Juninho [Pernambucano, sporting director] has asked for in any case.
"For the moment there is nothing done, but the door may be ajar thanks to Jean Lucas, who has just arrived.
"He [Ndombele] is a pragmatic boy, meaning that he didn't say, 'I'm leaving tomorrow, for sure'. He has been in demand from big clubs.
"When the biggest European clubs are knocking at your door, you have to listen.
"There is no deadline. At the moment, Thiago Mendes is one of the players who are of interest to our recruitment team."