Sweeney took over in 2015. 5 years ago. When most of us already thought Chara had probably a couple years left. He has had loads of time to find a top pair left D to backfill Chara when the time comes, and has even been given extra time by Chara sticking around & being effective for as long as he has. There's really no excuse for the fact that he has nobody to fill that spot in the organization AND on top of that has now let Krug walk.
I guess so- I have trouble blaming him for that. The Chara situation is and was a bit weird. As we have seen, Chara did not have a couple years left in his own mind and I doubt he even considered retiring. Then there is the whole He is Chara, Big Z, the Captain, first ballot HOFer, Bruins legend angle and many people have been saying for the past few seasons that 'he is still a #1 D man; best value in the league' etc. etc. So I am not wanting to hang that on Sweeney so much except that he might have been a little too soft on that score.
To me the Krug thing is separate. Chara or no, replacement for him or no, Krug should not have been retained at that term and salary regardless of the bigger situation. If Don does not get a Chara replacement- to me that is a top 4 LD quality, not necessarily a true #1- to partner with McAvoy or Carlo, then yes it's a fail.
That is not creating a hole, though. Rather, he just need to address filling the hole created by a) a player reaching the end of his career and b) deciding a player is not value for money/term being asked. Those are things every GM has to deal with and it is not really of Sweeney's making in my opinion. That does not let him off the hook for having to address the cirucmstances.