People keep saying this, but it's just not true. A team having the year the Avs were having in 2013, are not trading a very important part of that team (Stastny), who with Landeskog and MacKinnon formed a very formidable 2nd Line (because remember, O'Reilly and Duchene were lighting it up on the 1st line).
Show me one team in the past who is not only on their way to the playoffs, but also competing for a Division Title, trading away a player of the SAME caliber and importance as Paul Stastny. In the past some have (laughably) offered up Douglas Murray and Ryan Clowe as examples, but neither provided the same important role, nor was overall as good as Paul Stastny.
Why trade him away for futures (and in a year where people didn't get much at the trade deadline)? Are some of us really operating under the assumption that whatever the subpar return would have been, that we'd be in a better spot now? Plus, what happens to that year if the Avs DO trade Stastny? Why, it creates another hole. Either O'Reilly is moved back there, ending a offensive pairing that was dynamite (Duchene/O'Reilly) or they put MacKinnon back at Center, which wouldn't have been that great, because A) He was still very green at that position in the NHL, and B) it creates yet another hole on the 2nd Line RW side. On top of all of that, you then have to deal with the perception it creates in the locker room, that while this season is good, you don't believe in the group and it's better to plan for the future.
No matter what, trading him away at the deadline was not a mistake. Perhaps not trading his UFA rights could have been, but who's to say, the Avs believed that they had a good chance at re-signing him.