With the decline in Osimhan's performance, the price of his quality has decreased because since Napoli was left by Spalletti and became chaotic so that Osimhen did not appear more productive again, if last season Osimhen was able to appear impressive, several clubs would be interested even though the price was more than 100M.
The price of Osimhen has decreased. If you take a look carefully, his previous market value was €120m, it is only €100m now. I think the price of Osimhen can increase again if Napoli can perform better in the next season. I assume, Napoli can finish in UCL zone under Conte's management.
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After Spalletti left Napoli, Napoli never played with their best level again. Only Spalletti who knows well how to manage Napoli players. It may be caused the squad of Napoli was built by Spalletti, so it is developed around his tactics. The new coach of Napoli may need to adjust their tactics with the capability of Napoli current players. Antonio Conte must be aware with the capability of Napoli current squad, he mustn't be egoistic to apply the tactics.
Maybe when he gets a new club for example from the Premier League then his appearance will be a little different again where he could have a greater career there, which is the problem Napoli priced a high price below that price Napoli did not want to sell it some other big clubs certainly did not want to spend more money just because of Osimhen.
Chelsea is the most club that is very serious to sign Osimhen. But I don't think it is a good idea if Osimhen joins Chelsea because Chelsea is just an average team now. If Osimhen wants to win trophies, he is better to move to PSG. PSG also wants to sign him with high fees, but their offer is still rejected by Napoli management. If Osimhen really wants to join PSG, Napoli management may consider to decrease the transfer fees with certain agreements.