A little bit surprised by Fish tbh. Any match against a tall server like that can become a lottery, but certainly I have seen him handle what Isner throws at him, for example...and Isner is a much tougher player than Olivetti.
Credit to Olivetti for a career-best win, but he has a lot of work to do before he can play with the big boys on a regular basis. Evidently the serve can be a strong base for his game, but he really lacks consistency on it at the moment. He has a good backhand, and some nice touch at the net...but that is about it. Not top 100 material at the moment, before anyone jumps on the bandwagon.