 Despite achieving great regular season success, culminating in the 1978–79 campaign in which they finished with the best record in the NHL, the Islanders suffered a series of letdowns in the playoffs.In both 1976 and 1977, they lost in the semi-finals to the eventual champion Montreal Canadiens, and then suffered an upset loss to the Toronto Maple Leafs in the 1978 quarter-finals, on a game-winning goal by Lanny McDonald in overtime of Game 7.Then, in 1979, the rival Rangers defeated Arbour's Islanders in the semi-finals 4–2.