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I think it would be better if they brought Mane to the team instead of Kane transfer. Mane didn't show his best game last year. If he had believed in him this year and had managed to adapt Mane to the team, Tuchel might have considered a better option. However, I think there is a stance against Mane in the team. He never got on well with some players. That's why he's considering leaving the team.
Tuchel seems to have no more hope for Mane after seeing the game he gave last season.
We ourselves also know that Mane doesn't provide many good developments and he doesn't even look very enthusiastic in every game he plays.
In my opinion, it is only natural that Thomas Tuchel is looking for a player who can significantly provide playing skills like Kane, considering that Kane can still be relied on even though he is now 30 years old.
The only question is the same as you said, does Tottenham want to let Kane go because there are already enough clubs eyeing him but failing to make a deal with Tottenham.