Cut versus keep will work itself out - as our squad is full of highly talented individuals all desiring playing time - those not getting enough time will, ideally look to move on their own. The key though is to have pressure on everyone to perform due to highly talented competition.
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That said:
Zinchenko - not quite talented enough. Sell.
Mendy - extremely poor on defense. Hugely talented going forward. I'm not sure how he fits our squad. Perhaps he can improve defensively or play as an outright winger.
Jesus - does not seem to be good enough to replace Aguero. A talented player for sure - but needs to improve if he's going to be our go-to striker once Aguero retires.
Gundogan - our midfield is packed. And although Gundogan is very talented - he's someone who should play in the hole - and he's not a pivot. He's best as a deeper lying midfielder paired with a true defensive stopper - but that's not how we line up. Probably sell Gundogan, both for his sake and ours.