Lyon have sought to deter clubs from pursuing 16-year-old winger Willem Geubbels by valuing the young Frenchman at £62.5m - more than £2m for each minute of Ligue 1 football Geubbels has played.
Geubbels made his senior debut as a late substitute against Dijon in September, becoming the first player born in the 21st century to appear in the French top-flight.
He also came off the bench against Amiens in December, but has only played 31 minutes of game time overall and has not even been in the Lyon matchday squad in 2018.
There are concerns that Geubbels could leave the Stade de Lyon when his contract expires in summer 2019, having turned down a new offer earlier this season.
Lyon president Jean-Michel Aulas told French newspaper L'Equipe that Geubbels will not be allowed to leave the club on the cheap, and mentioned Ligue 1 rivals Monaco as another club interested in the player's signature.
"They have just cashed €300m or €400m, so they will pay for Geubbels," said Aulas, quoted by FourFour Two.
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He was alluding to Monaco's transfer business last summer, which saw Kylian Mbappe, Bernardo Silva, Benjamin Mendy and Tiemoue Bakayoko leave the Stade Louis II for pastures new. Mbappe is expected to cost Paris Saint-Germain €180m when his loan move becomes permanent at the end of this season.
"It is the end of his [Geubbels] contract in 2019," added Aulas. "If Monaco makes an offer of €70m we will be disappointed because we believe [in Geubbels] a lot. We are reassured by his valuation."