have you watched them this season?
Yes, a few times.
They failed their hardest test so far in Shakhtar. They beat Lazio who I think will finish sixth 4-1 after going down a goal then scored 3 goals in 5 minutes after Lazio self destructed.
Milik is out for 4-5 months and they have no replacement.
Sarri is an excellent manager but he isn't backed financially and they haven't improved the squad this summer. Mertens and Callejon are both 30. With Milik out they will both play a lot more.
After the international break they have Cagliari at home, then in a week Roma (A), City (A), & Inter (H). We'll see their level. They are a great team and will challenge as they've done the past few years but won't win it.