Getting back to 1986:
That's such a fascinating series. It really is the dividing point between the young, high-flying, offensive machine Oilers of 1981 to 1986, and the more mature, disciplined, better-balanced Oilers of 1986 to 1990. It was also the end of Paul Coffey's six years of happiness in Edmonton.
Calgary had the right game-plan and played it to (almost) perfection. The most remarkable thing was that the Flames won 3 of the 4 games in Edmonton, and almost won 4 out of 4, but for Andy's overtime winner. Anyone who thinks Steve Smith cost them the series is forgetting that rather inconvenient fact. Not once did the Oilers ever have the lead in the series (they trailed 1-0, 2-1, and 3-2). Gretzky was totally silenced in games one and two at Northlands (which never happened!), but did go on to play really well in games three, (esp.) four, five, six, and seven. But Kurri couldn't score and Paul Coffey was poor in general. (Easily overlooked is that Craig MacTavish scored 4 goals in this series, second only to Anderson and Gretzky.)
Rarely has one series shifted the balance of competition between two clubs so much: The Oilers' record against Calgary in the 24 regular season games prior to this series was 19-2-3. The Oilers' record against Calgary in the 24 regular season games after this series was 6-15-3.