We're all just hypothesizing right now since we don't have a crystal ball, so I admit I could be wrong. I think this is an interesting discussion though, so I'll just break down all the the reasons why I feel the way I do, since I've talked about them all in separate posts, and it's more of a cumulative thing than one reason being the deciding factor by itself.
I've thought about this for a long time because I could see the writing on the wall, especially after drafting Nate, but I've never really organized my thoughts all together. I was gonna start a new thread about it, but it's basically the same topic so I might as well post it here.
My Preference
I think the Avs need to become a little more top heavy, and make their franchise players in Duchene, MacKinnon, and Landeskog their go to players, and make sure they are being played top minutes in a go to role.
This also includes playing the more or less secondary skill wingers like PAP and Tanguay in top two line offensive roles. Guys like McGinn and Downie are versatile and don't necessarily have top end skill, so they can play in different roles through the top three lines depending on the situation, and whether the lines need shuffling.
The Linemate Problem
This is a big part of it. We've seen in the past that Duchene needs skill wingers to play with, and is kinda picky with who he develops chemistry with. The only player he's really developed any consistent chemistry with is PAP. Stastny also has displayed that when he doesn't play with a skilled sniper, he underperforms. Having a PF type benefits him as well, but it's really the sniper aspect that he benefits from as a playmaker, and the skill aspect that he benefits from playing a give and go game.
This basically means they need two fairly highly skilled players (they don't have to be dynamo's but somewhere around a PAP level) for each of them.
Then you're left with your 1st overall franchise center Nathan MacKinnon. Surely he has to play with a similarly talented player, or you're wasting him as a 1st overall pick. If they had expectations of him contributing at a lesser level playing in a lesser role, they should have drafted Jones or someone else.
Now you need three talented wingers. So far only PAP has developed chemistry with Duchene, so they'll be tied to the hip for the most part, and as of now going into the season, the guys Stastny has had chemistry with are playing on other teams. So at best we're assuming he'll find chemistry with someone.
All of this makes balancing the lines tough in and of itself but it's only one aspect.
The Star Player Role
This is another big factor. We've seen it time and time again in history. In order to win a cup, your star players have to be your go to guys over the course of a season and the playoffs. You can get away with them slumping and other players stepping up in spurts. This can get you through parts of a season, or a round or two in the playoffs, but it's not going to get you through an entire season and all the way to the Stanley Cup.
Highly skilled offensive players benefit the most playing big minutes, and they relish playing in the go to role. All players benefit from playing more minutes because it helps them get into a rhythm in a game. Relishing the go to role is something usually isolated to "skill players" because they have spent their entire time from a young age all the way through their NHL years, being the best players on teams, and have developed a certain amount of confidence/ego in themselves and desire to be among the best.
When you take that role away from them, even just a little as far as putting them in a 3 line rotation, and less or 2nd PP minutes, it disrupts their rhythm and puts a little chink in their confidence armor.
Three Offensive Centers vs Top Heavy Two Lines
This is more of a philosophical idea to an extent. One theory is that when you have these three offensive lines like this they don't push themselves as much. It's similar to the Star Player Role aspect that I mentioned above. They don't have to be the go to guy because there's eight other players that can chip in. It can cause players to sit back the way the natural response can be to sit back when a star player comes back from injury.
So instead of three offensive lines which is the way it looks on paper, you have three lesser lines. Possibly watered down because you spread out the talented wingers. All three lines aren't all playing and producing the way they would if they were a go to 1st or even 2nd line.
This is all due to the linemates, the role issue, the minutes issue, all of these things. So with all of these things does the production and end result really match what you hoped for with three lines, or are you using three lines to get the production you might have with two, and removing the option of having your 3rd line have success offensively playing a different style, and focusing more on specialized role situations and defense.
There's no way to prove it, but if there was I would bet all my money that a top heavy two lines based around Duchene and MacKinnon along with an O'Reilly 3rd line playing a lesser role, would at least match the offensive production of a three offensive line approach with Duchene, MacKinnon, and Stastny.
With this matched production, they'd also have a 3rd line that the other didn't, that can focus more on specialty roles like matchups, and just approaching the game from a different style where they take what's given to them and feed off turnovers, rather than pushing the play trying to "create" offense.
When your offensive lines get shut down playing against a smart defensive team in the playoffs, this is where you need that X factor and other guys who play a different style to get your through to the next round by chipping in offensively because they approach offense from a different mindest and they don't get "shut down" and stifled the way an offensive line would.
O'Reilly vs Stastny
This is probably the big thing for most people, and what the thread was about, but in my mind as you can see it's a little more complicated than that. Other things are more important as to the reasons they should focus on for making the decisions they will make.
As for the choice between the two, as I've mentioned the Avs should have a top two line appraoch, and let the 3rd line play a lesser role. It shouldn't be devoid of offense and it won't with O'Reilly, and Downie and whoever. They're underrated offensive players, and have both smarts and skill. Downie also plays a good disrupter role, which most of the time you want to keep in a fairly selective role, rather than sending them out there for 18-20 minutes a game to fly off the handle.
This is something I haven't touched on in other posts, but I don't get a sense Stastny would play a more defensive role as a 3rd center. I don't think the team would ask him to as much either. He's an offensive guy, he's approached the game that way his entire NHL career. He's good defensively, and could play a defensive 3rd center role, but with him on the team I think both he and the coach will be looking for him to push the action.
O'Reilly on the other hand has shown an elite defensive ability, and approached the game from a defensive standpoint. In his third year when he pushed the play a little more and scored more points, he still focused more heavily on his defensive zone play, and neutral zone turnovers than Stastny does.
Ideally what I would like to see is for them to give O'Reilly his $5M+ so they get that issue out of the way. Then reign him back a little in terms of pushing the play like he did in his 3rd year, but let his confidence from that success, and Roy coach him to play a legit two way game with a little more offense than he generated his first couple year. Great defense, specialized situational play, and some offense and create offense. I have no doubt O'Reilly could do this playing in a lesser role.
This satisfies the selective roles they need to fill to be competitive over the long haul and in the playoffs, and keeps some offense on the 3rd line as well. Most importantly it removes the 3rd line from being a threat to take away minutes, linemates, and the go to role from the top two lines.
There's also a secondary option of keeping O'Reilly on wing, and finding another 3rd line center via trade, UFA, or from within but I don't like that option as much.
Cup Winning Teams
Every year we see it in the playoffs. The team that wins the cup gels at the right time, their star players are their go to guys, and they keep things simple with everyone playing their roles. The defensive guys play their roles, the offensive guys play their roles. The special teams roles have to perform well especially the PK. The defensive guys have to chip in a little offensively, and most of the offensive guys have to play good defense even though they're not focusing on this aspect in their role.
The main idea though in reference to this situation is that everyone has clearcut roles, and this allows the star players to play in the offensive roles, and the 3rd line guys to play in their roles. One could say that a Stastny line could play this lesser role, but I just don't see that happening. It will be too tempting to coax more offense out of Staz, and it will play in an "offensive role." Teams just don't win the cup trying to outscore everyone, they need those lesser unappreciated roles filled from more than a 4th line playing five or six minutes a game.
Cap Space
This is a lesser issue and may not come in to play that much, it's hard to tell. At least for the foreseeable future it shouldn't impact their decision to keep O'Reilly and Stastny. They have the cap space, the cap should go up next year and every year after, while they have Duchene and Landeksog during that time on fairly cheap numbers.
Where it might get tricky is when MacKinnon is due for a raise with a much bigger cap, and how they plan to ice a competitive D. Paying Varly if he establishes himself in the near future, or another top goalie if he doesn't work out, could play a hand as well.
It also could make it very difficult to afford a dynamic winger as the finishing touch to their lineup. They'd be more or less set with their group after paying MacKinnon what he's worth, and paying a legit D Core and legit goalie what they're worth.
This is all down the road, but they need to plan for it now when deciding on re-signing Stastny especially. He's not going to sign a two or three year deal as a UFA.
The D
This also is a lesser issue than the main points above. The issue by itself is HUGE, but not necessarily in relation to what they do with O'Reilly and Stastny, or the three offensive center approach.
Where it might come into play is using one of Stastny or O'Reilly to package or bring in a D by themselves. At first glance it would appear that O'Reilly would have more value in trade. His QO, and price he might be asking for could change that. As could the price that rentals in general have at the deadline, in which case Staz could bring in a good young NHL D if a team already has a couple go to's ahead of them.
In a vacuum this is something you'd have to weigh as to what the better option would be. IMO though, with all the other reasons I've mentioned, and the fact that the trade value may not be too far apart, it's an easy decision to move Stastny for some help on D, even if it's not a home run return, or O'Reilly could have brought back more.
5th Year of Rebuild and Beyond
They're kind of at a crossroads in how they're building their team. The D needs a lot of work. They'll want to allow themselves the option to add a dynamic winger in the future or tweak the winger group. Most importantly though it's just time.
They can't be playing this wait and see game forever, and with Duchene taking the step he did last year, the selection of MacKinnon making him a big part of the future, the management re-shuffling, and with just the fan impatience at this point after continually missing the playoffs, and being a decade removed from Stanley Cup contention, they need to pick a direction and go with it. Go all in so to speak, and if it doesn't work out it doesn't work out, but they have to be decisive and try to make what they go with work.
Last Thoughts
It's a very complicated situation, and what really needs to happen for a Duchene/Mack/Stastny group to perform like some hope/think is for all these things more or less to go in a positive direction rather than what I'm worried about. That's why it's a cumulative thing.
Very much based on the odds of that happening, as well as most these things have proven themselves to be the case in history as far as my reasoning in the points above, I think you have to edge towards going with a more traditional top heavy approach, and cut ties with Stastny instead of keeping him as a 3rd center with Matt and Nate.
The decision to keep O'Reilly at center on the defacto 3rd line or at wing is a separate decision. They both have their merit as using O'Reilly in this role is a bit of a waste, and depending on how well he adjusts to the wing he may be more productive in that role. As I mentioned though, I think it suits the "team" much better to keep him in this 3rd line role, where he'll still be able to provide offense, and even used a bit more offensively than most teams 3rd lines, but play in a "role" where he focuses a lot on situational play within games and defense.
Keeping O'Reilly in this 3rd line role also allows them the ability to add a dynamic winger in the future to build on their top heavy approach. Adding this winger most likely won't happen with Stastny and O'Reilly on the team making semi big bucks. It won't work out space wise either and it will be tough to find an open spot.
If it makes it any easier what's better? A highly talented and productive Thomas Vanek or someone similar down the road playing next to Duchene with an elite two way center in O'Reilly centering the 3rd line? Or the less productive O'Reilly on Duchene's wing and the more offensive minded Stastny on the 3rd line?