I think McDavid on the strength of his sustained offensive zone time alone is our best defensive forward, add to that his really high takeaway numbers, defending through puck possession tends to be superior to actually being good defensively, and it's not like Nuge is substantially better than McDavid defensively if we are talking in terms of the occasions we are hemmed into our own zone.
What Rakell represents is a value contract, he's signed for 3 more years at less than $4M, compared to Nuge's 2 years at $6M, with some sort of raise after 2 years being likely. Rakell also has hit some marks that RNH hasn't yet, Rakell has a 34 goal and 33 goal season under his belt as well as a 69 point season. The two players are the same age, so we aren't getting any older with the deal, the difference between RNH and Rakell's career points per game is 0.08 (6-7 points pro-rated to an 82 game season) compared to the difference between Eberle and Strome at the time of trade which was 0.32 (26 points pro-rated to an 82 game season). It's fair to call this a downgrade, but it certainly doesn't seem to be a huge one, like the Eberle for Strome deal was.
Rakell is a really good player and really seemed to be blossoming in his 2 years prior to this season, basically every Duck has been terrible this season and its bared out in their point totals, I fully expect Rakell to bounce back. If we were to make the trade I wouldn't want Rakell playing C, to me it signals a permanent breaking up of the McDavid + Drai combo to run their own lines respectively, RNH provides a tremendous versatility and we really don't have many players of his ilk who can be utilized in any situation, that should be weighed heavily if we did endeavor to move him. I've watched a lot of Rakell, but no so closely to really pin down how much of a downgrade he'd be defensively, but IMO he was a good defensive player in any of the games I can recall over the past 3 years.
As an aside I'm a bit troubled by the amount of people in general who are ****-talking Nuge (more prevalent in GDT and PGT's than here) or want to trade him, cause of his recent down turn in play, basically no one is consistent through an 82 game season, people play way too hard into recency biases and should endeavor to be more balanced in their evaluations.