An achillies injury is likely to affect him more than an ACL. I think 9 months is optimistic. If he's well and truely knackered his Achillies we're unlikely to see again until the start of the 27/28 season.
As much as Slot has made a mess of this season, he's not had much luck with injuries. Isak, Bradley, Endo, Leoni and now Ekitike with really serious long-term injuries. You can't really legislate for that.
I saw a stat this morning that Ekitike, Wirtz and Isak have had a grand total of 88 minutes on the pitch together this season.
Something, Something, Something, Dark Side