As to the team's performance, the 67s have demonstrated they can carry the play and win games against quality opponents. Why they are so inconsistent in doing so, and why they more or less stopped doing so down the stretch starting with the Erie game (not counting games vs. Peterborough, Barrie, Niagara), can be a result of several factors but personally I think that stretch of play was ultimately unsustainable due to not having the "right" personnel, and coaching decisions.
I think the 67s are a good team, but they are outmanned in terms of depth at F and D against stronger top to bottom teams like Brantford, particularly in terms of roster construction for a playoff run. The 67s lack size and physicality in their top 9. The smallish, speedy guys are able to pressure the puck and cause turnovers, but when push comes to shove they are inconsistent in their ability to get to the net and generate scoring opportunities from the prime areas. The desire is there for the most part from Pinelli, Kressler and Gerrior, so I'm not faulting that...but at some point its simply a size and strength issue.
In terms of coaching, I'm not going to speculate on whether DC has "lost the room" or not, as I/we may never know one way or another. However, I do see a fairly poor PK and PP down the stretch, lack of discipline from the leadership group, inconsistency in terms of effort, and some questionable D pairings, forward lines and allocation of playing time.
@OMG67 mentions above that Mayer is able to play 30-35 minutes/game. I certainly don't disagree, but when Ottawa's backs were against the wall last year vs. Peterborough, DC continued rolling out three D pairings (including a Mews/Marrelli pairing - both 16/17 year-olds) when he had Jack Matier and Pavel f*****g Mintyukov available, so I don't think he is going to suddenly decide to shorten his bench. I just don't see it. #2 on D plays a ton at ES and on the PK and consistently gets walked or caught out of position in the d-zone. Why is he playing so much? That one I can't understand.
The special teams play, lack of discipline, inconsistent effort, and line/D pairing construction and allocation of playing time falls on the head coach, and in my personal view he shouldn't a passing grade at this point. Note that all of these issues are possible even in a scenario where DC still commands the respect of his players (or in a scenario where he does not). I just don't see this team as being as good as the sum of its parts, and it turns out the parts probably weren't good enough to make a run anyway.
Regardless, Ottawa isn't exactly in a bad position at this point. MacKenzie may be in a groove, which will make things difficult for Brantford. We'll see what this evening brings with a probable dead crowd.