I'd sell without even buying a replacement. I really liked him when he joined us, but those last 1,5 years with him being a starter were a true shitshow. Not really a fan of Eric Garcia, but at least he is still young and can develop. Can't rely on a guy as experienced as Lenglet but prone to so many mistakes. He is also very slim and physically weak for a CB if you consider that he isn't fast either. We need the money more than we need someone like Lenglet. Eric Garcia is cheaper and has similar strengths/weaknesses. I don't consider him a downgrade given the circumstances.
EPL clubs have money, so I wouldn't sell him under his current market value which is 25M atm. This club never was good at selling, but the board shouldn't give in if someone wants a discount. Can't afford that.