This might be the big one for Grealish really - we need so many other positions filled too that signing him instead of (realistically) two other players at, say, full back would likely be detrimental to the team, especially if we're in Europe.What's the current wage/turnover situation? I think if we get into any kind of European competition, we're limited to 75% of turnover going on wages.
There's the option of signing him on loan again and City paying a big chunk though, but doubt they'd want to do us that favour.
Keep Ndiaye regardless.