Colorado will have ~$3.8M in cap space when Miles Wood comes off LTIR (in the next couple games). That means heavy retention on Nelson, which is going to drive the price up even further. O'Reilly would be doable if the Avs freed up a little more room, but the club has other issues that need to be addressed with this cap space. Not to mention, there's a ton to unpack with that player and the team in question.
If Colorado makes a move at 2C, I am confident Casey Mittelstadt is going the other way in the deal. Mittelstadt has been a colossal disappointment; his rise and fall has been more rapid than Ziggy Stardust's. The guy was a perfect fit the first 50 games (incl. playoffs), but his last 30 have been so disturbingly poor that he was arguably deserving of healthy scratches at times. Did I mention Colorado traded their most premium controllable asset for him?