The Italy international has struggled for form and fitness in his first season in England.
But Slot says the signing from Juventus can still have a future with the champions: "Does he have a future here? Yes, definitely he has, yes. Definitely. I think everyone playing for us over here has a future over here.
"Next season, if he comes back completely fit, which he has hardly been for the first half-season but then afterwards he became fitter and fitter. The next steps should have been playing time, which I couldn't give him.
"But I can give him playing time in pre-season, so he can build himself up and then go even further.
"That was also one of the things, if you do so well – and it was the same with (Ibrahima) Konate and Virgil (Van Dijk) – some people say maybe you should rest one or two once in a while.
"I know for sure the chance of winning when I play them both is particularly high. So why would I take the risk of rotating? But yeah, pre-season gives (Chiesa and other fringe players) the chance to show themselves again."