Chelsea have been warned that allowing Callum Hudson-Odoi to join Bayern Munich could leave them cursing a deal similar to that which took Jadon Sancho away from Manchester City.
Back in 2017, the reigning Premier League champions saw a reluctance to offer regular game time to an exciting academy prospect lead him to seek a new challenge in Germany with Borussia Dortmund.
Sancho is now a Bundesliga title challenger and senior England international, with his potential being given the best possible support at 18 years of age.
A fellow teenager, Hudson-Odoi, is now being linked with a similar switch, with Goal having revealed that Bayern have a £30 million ($38m) offer on the table.
Chelsea are reluctant to sell and a former Blues striker has urged them to do all they can to retain the services of a prized asset and tie him to fresh terms.
Cascarino told The Times: “Bayern Munich's interest in Callum Hudson-Odoi should tell Chelsea all they need to know.
“The 18-year-old is clearly a special talent and they should be doing all they can to stop him joining one of the biggest clubs in Europe.
“Transfer fees are obscene for teenagers but Chelsea should look farther down the line.
“Just look at Jadon Sancho at Borussia Dortmund.
“Manchester City let him leave and now he is starring for the Bundesliga leaders domestically and in the Champions League.
“Chelsea must resist the temptation of selling Hudson-Odoi this month and try and persuade him to sign a new long-term contract - his value and ability is likely to only increase.
“There aren't many players who can skip past players and deliver such brilliant crosses as he did against Nottingham Forest on Saturday.
“He set up Alvaro Morata for both goals and was comfortably the best player on the pitch.
“Chelsea have had little success in establishing their academy players in the first team, which should make them even more determined to keep Hudson-Odoi.
“They know how important it is to their fans to have a home-grown player star for the first team - just look at how the supporters adored John Terry.”
Hudson-Odoi made his Chelsea bow during the 2017-18 campaign, with a debut handed to him in an FA Cup tie against Newcastle.
This term he has taken in a further seven appearances, with a first competitive goal scored in a Europa League clash with PAOK Salonika in November.