Sarri will be fine if he's given time. Question if he'll get it at Chelsea but he'll certainly get more than the 3 weeks he's had.
What a lot of people are forgetting is that Chelsea will keep their top players fresh for the league. The likes of Hazard, Azpilicueta, Kante, Courtois (if he stays) won't touch Europa football, they will be well rested and that will make a big difference over the season.
Still think Chelsea will manage a top 4 finish.