Battle of Alberta – Wikipedia

The Flames defeated the Oilers in the 1986 NHL playoffs; game 7 was decided when rookie Oiler defenceman Steve Smith accidentally scored on his own goal, which pushed the rivalry to a new level. The Flames were favoured in the 1988 playoffs , having won the Presidents’ Trophy , [30] but the Oilers swept the series and eventually went on to win the Cup.

https://en.wikipedia.org/wiki/Battle_of_Alberta