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I also personally think that if Mbappe leaves PSG and joins another team, then PSG will break the basic structure of the team. Because Kylian Mbappe is one of the best players in the attack, it will be very difficult for the team coach to fill that need by replacing him with another player.
That's why PSG doesn't make it easy for any club to buy Mbappe, after all, I'm sure that if there are other clubs, including Real Madrid, want to accept the price offered by PSG, the PSG management will still raise the price again to be able to have the highest bid and make it difficult for Real Madrid to brought in Mbappe.
Maybe many PSG fans don't really like Mbappe, but basically Mbappe plays a very important role in the PSG squad.
If next season the contract runs out and there is no further extension then I'm sure PSG will experience a decline in playing performance because several attacking players who can be relied on have left one by one.