Yep, that's what they mean.
Although I wouldn't have put it quite like that myself - a check mark is a positive sign to me.

Vergleiche abhaken.
Siehe Wörterbuch: abhaken
„Etwas abhaken“ bedeutet immer, dass eine Sache im negativen Sinn erledigt ist.

I think I've already heard this expression used both for "write sth. off, forget about it" and for "tick the box" (i.e. "mark the task as done and dusted"). I'd say the latter is more common, the former is more usually Siehe Wörterbuch: abhaken

So depending on which team this is about it can either mean that the team has no chance of winning anything this season or that they are already so far in the lead that nothing much can happen to them. I'd say it's probably the former.

You're right. The verb is "abhaken". Tick off. I agree with Dragon and Gerd. It's rather a bad sign for the team and its fans.