Broberg will be in the opening roster.

Why are you so sure?
Firstly, if we keep Broberg in the first team, then we need to drop Samorukov or Murray to the AHL through the draft with refusals, this is a big risk of losing them, especially Samorukov. Is it possible that our system systematically for several years meticulously led Samorukov to the base, in order to lose him for free through a draft bounce at the beginning of the season, exactly at the moment when he came to a state where he could play in the main team, even if only the seventh defender in a limited role so far , but this is only the beginning. It seems to me that this step would be a bit reckless.
Secondly, after watching two pre-season games, I had an opinion about the game of each of the three defenders. I understand that a sample of one game for each defender is not enough, but still the main conclusions on the game of each can be drawn.
Broberg is still too raw at the moment to play in the NHL. My opinion, for him and for his development at this point in time, it is better for him to play in the top pair of the AHL, and get the lion's share of the time in equal compositions, in the majority and in the minority. After the deadline, when you can safely drop one of the defenders without fear of losing, for example, Murray, and raise Broberg to the playoffs in the third pair. Based on the results of the pre-season match that he played with Seattle, I can note the moments of his game. The ride is great, no question. His connection to attacks and individual passes deep into the attack zone, this is his trump card undoubtedly. He definitely needs to pull up the actions at his gate, he is not particularly quick.
Samorukov. He didn't show anything special, but he didn't make any blunders either. The game was pretty gray. I make allowances that he is still young and this is only the beginning of his journey to the NHL. In general, a good moment that no mistakes were made in defense.
Murray. You can see the calmness in actions, you can feel the experience behind you. In general, a calm game without panic. May be useful in the third pair. Experienced, in the golden age for a defender, he can still play for four years if injuries do not affect his career.

TL;DR

"Why are you so sure?" It has to do with bonuses in his contract. If he's on the season opening roster the bonuses don't count against the cap and if vested can be pushed to next year. If he's NOT on the season opening roster then when he's recalled during the season they have to account for his AAV PLUS his bonus money. So it's a guarantee he'll be on the season opening roster. Holloway too.

"Broberg is still too raw at the moment to play in the NHL." That's your opinion, not many share it. He has clearly been better than Samorukov and Murray so far in pre-season action, and he has a higher ceiling than both. I think he's pretty much a lock for 3LD from the start.

At the expense of bonuses, I definitely agree, Broberg will be in the starting lineup, this is obvious.
But this means that Samorukov or Murray must be put through a waiver draft. Losing Samorukov for free is a bad decision. Holland decided to add experience in the person of Murray, in principle, in the first game, Murray showed himself as an experienced and stable defender. At the moment, he looks preferable to Samorukov. But losing Samorukov for free is bad. And to be honest, I was sure before the acquisition of Murray that Samorukov would be the seventh defender. And for our system in terms of prospects, this would be the best solution. And an experienced defender could be purchased before the playoffs. But now I'm afraid we will lose Samorukov through refusals.
And yes, I probably completely explained my position clearly. I also believe that Broberg is stronger than Samorukov and Murray, but given that Samorukov needs to be drafted through the waiver draft, I am afraid of losing him for free, this is the main reason why I have him higher than Broberg.

I understand not wanting to lose Samorukov to waivers, but I think the cap issue is far more pressing for Holland. Besides, we know the club is high on Niemelainen, and he doesn't require waivers - so if they lost Samorukov it wouldn't be the end of the world.

I think Broberg stays and one of Murray & Samorukov hit waivers. Camp will decide which.

I agree. In the first two games, in general, you understand who is who.
Since we are talking about the left edge of the defense. Overview of left backs.
Fist is top4.
Murray is an experienced, calm, potential third pair of defense, but according to the experience of previous years, he is highly traumatic.
Samorukov is generally a capable defender. At the moment, the seventh defender.
Broberg is a great figure skater, a combinator, at the moment he is not quick in defense, he is losing his position, this shortcoming must be corrected. At the moment, the potential of the third pair. Two years later, a top 4 defender.
Niemelainen is a great power defender. In two preseason games, he was a dominant defenseman. When he was on the ice, silence immediately set in on defense, he confidently cleaned up all the dangers. He is already better than Samorukov, Murray. At the moment, he could easily play in the third pair, but given the opportunity to lower him this season without refusal, he will spend most of the season in the AHL. In terms of potential, Broberg is higher than Niemelainen, but Niemelainen, in principle, is already a ready-made chic defender of the third pair, who in another team, where there is no Ners and Broberg in front of him, could easily play in the second pair.

Next year I see protection like this
Nurse Ceci
Kulak Bouchard
Broberg Desharnais
Niemelainen
It is obvious that Samorukov has no place in our defense. But to lose a promising defender on the rise of a career, which was spent on how many years of development in the system for free, is a damn shame.