1. Four-game series sweeps: There have been 25 four-game sweeps in the first round of the NHL playoffs since 1987. Teams that win the first round in a four-game sweep won 11 series and lost 14 series in the next round. 2. Seven-game series: There have been 52 seven-game series in the first round of the NHL playoffs since 1987. Teams that win a first-round series in seven games won 23 series and lost 29 series in the next round.