I'm conflicted on Dach.
On the one hand, you can look at Caufield literally from last season where he didn't look like the same player or scoring threat he was in the past (after surgery). It would have been really easy to throw our hands up, expect that it was going to continue to that way and give up on him.
On the other hand, Caufield has been a scoring threat his entire career and has consistently shown that. He had a form to return to. Dach hasn't really done anything other than the flash he showed in the second half of his first year here. We have an idea of what he could be (or now, could have been) but that's about it.
This is hard. Do you cut your apparent losses now or wait and see for yet another year? 2C is a super important position on a hockey team and we cant let a guy who's clearly floundering keep his spot without impunity for a whole season and a half if we expect to climb out of his rebuild.
It's the easiest decision to make.. you just keep playing him, coaching him and working with him this year. At the end of the year if his play hasn't come around to an appropriate level; then you send him home for the summer with a clear set of instructions on what he is to improve upon.
If Dach does or doesn't find his form by the end of the year, the calculus doesn't change, this group should be looking for improvements at the center. Whether it's finding a better 2C than Dach or a better 1C than Suzuki.
If you find an improvement or Dach comes in with the mindset and play to securely claim one of those spots, he is still an RFA after his contract ends NEXT YEAR, so you'll have plenty of runway to see if he's a top 6 fixture, or a guy in your middle 6, who will still provide value through his size, skill and ability to play wing or center. His cost for extension would remain very low.
He is not blocking a single internal option this year.
There is not a single external option that is a viable option right now and if there was, if he was playing well or not, it makes no difference, they should be looking at whether the acquisition cost makes sense.
Cutting losses with Dach right now is the singularly most stupid conclusion anyone can draw. You won't get what you paid to get him. You would be panicking far too early after a major injury especially in the context of a team that has several players not delivering to a previously established level.
You can only lose moving on from Dach prematurely.