To further the point of avoiding using our 1st on a LD...
In a couple years, Klefbomb & Nurse will almost certainly be on our 1st & 2nd pairing. Not to mention, we also have Sekera for at least two additional seasons as per his NMC. I'm going to assume Chiarelli will make an effort to move Sekera in the summer prior to the 2019/20 season to open up more cap space.
Given two full seasons of development, we have these prospects in the pipeline:
Reinhart - Due to waiver eligibility, he'd need to step into at least a #7 role, which might be raised due to Sekera's injury. Likely to be claimed by Vegas, however.
Oesterle - Prior to Sekera's injury, it looked like his best interests were to go elsewhere. He is someone that, if Reinhart is gone, would take hold of a bottom pairing job.
Simpson - Today, I think he is a decent call-up option, but don't know how I feel about him as a regular on the roster.
Jones - Well-rounded game with great attributes.
Paigin - He seems to have a really high ceiling, but time will tell how he translates his game to NHL rink & pace.
Lagesson - Size, speed, physicality. Defensive D who definitely has a chance.
Niemelainen & Cairns - Both seemingly long-shots.
My conclusion
In the short term, one of Oesterle or Reinhart could cover the bet. Longer term, I think after two full seasons of development one of Jones, Paigin, or Lagesson can cover the bet as a bottom pairing D. Lets just continue drafting LHD with out middling picks, our scouts have been doing a pretty solid job the past couple drafts.
Compare that to other positions.
Left Wing
Lucic is a lock for the top 6, and that's all we can be sure of. Will Maroon re-sign with us, and for a reasonable rate? Will Caggiula be a consistent point producer in the top 6? Khaira, Laleggia, and Benson (injuries!) are all promising prospects. A Robertson/Vesalainen/Kostin pick would give us a sense of security for this position though.
Center
We can't be sure that Nuge will be here when McDavid's contract kicks in. Without him, we have 2 centers in the top 6, and 2 centers in the bottom 6 if you include Khaira (who I imagine won't be counted on to step in as anything beyond 4C). We have a decent pipeline of checking centers in Gambardella, Vessel, and Rasanen (Platzer is AHL depth at this point). But top 6 center prospects? None. Thomas would be tremendous value. Smart two-way player that, if he can't play 2C, we'd be happy if he could play 2RW. If not even that, I'm sure he could at least be a long term cost effective 3C.
Right Wing
I think we can all agree Eberle is not a long-term fit with this club. Due to cap, and Nuge having more value to the team. If you run Draisaitl 1RW, things aren't all that bad. Puljujarvi is essentially the only bonafide top 6 RW prospect we have, and we can't count on him to be ready for next season. We're not entirely sure what we have in Slepyshev, but he's at least a middle 6 RW. He can play 3rd line minutes just fine, but who knows if he can become a staple in the top 6. For bottom 6 players, we have Kassian, Pakarinen, and a couple maybes' (Pitlick/Foo). We don't have any good prospects outside of the NHL team. If we draft a RW, grab the best shooter who has a knack for finding open space, as Draisaitl & McDavid are excellent pass-first type guys.
Right Defense
This position is clouded in mystery. We need an answer for RD today, I imagine Chia figures something out via trade. Acquiring a 2RD would keep Benning at the bottom pairing, which is good for depth. Benning himself might even become a 2nd pairing guy. I wouldn't count on Bear or Mantha being 2nd pairing guys, but would be ecstatic if they become reliable options for the 3rd pairing. Would be happy with a Timmins pick, as it would give us stability for defensemen prospects.