Mirth exactly. Internal boosts and internal set backs can't be entirely foreseen, someone like Havertz for instance could go supernova this season and score 20+ league goals or he could dry up and score less than 10. We just don't know. There is also injuries, we didn't expect to lose Timber for the season this time last year. That can happen to anyone. Plus we have the perennially injured like Partey, Jesus, Zinchenko, Tomi, etc who'll likely miss plenty of the season. You can't rely too much on internal improvement as its usually more a case of standing still.
