By Harry Chiel
Every so often, a playoff series in the NHL, MLB, or NBA will be fought between a team that has just come off of a sweep and a team that has barely survived a competitive 7-game series. While the latter team is still battling and exerting itself in games, the former will be resting, recovering from the 4-game series, and preparing for the next round. Just this autumn, the Detroit Tigers handily swept the New York Yankees, while the San Francisco Giants went to 7 games against the St. Louis Cardinals. The Tigers wrapped up the LCS on October 18th, the Giants on October 22nd. Two days later, the Fall Classic began. Similarly, in 2012, two NBA playoff matchups also had this same structure (OKC vs. LAL and SA vs. LAC).
Each time a series like this occurs, we are given two contrasting arguments by media figures. On the one hand, the team that swept has had ample time to recuperate from injuries, rest their bodies and arms, and watch video on both potential teams it could face. On the other hand, in the large gap of time between games, the team could have “lost momentum,” somehow dissolving the focus and chemistry that had led to the team’s initial success.
It is difficult to conclude which explanation is more legitimate, given the small sample size and numerous problems with asserting causality. Nevertheless, I reviewed instances where this type of matchup has occurred, in order to see if any clear advantage or disadvantage manifested itself.
Across the NHL, MLB, and NBA, and looking only at matchups where the previous round was also a best-of-7 series, this scenario has only occurred 29 times throughout history. The team that has swept has won 20 out of these 29 occasions, and has needed, on average, 5.3 games to defeat its next opponent. This is not too distant from what one would expect; the teams that swept, in general, have better regular season records, so they tend to be stronger than the opponent who has struggled to emerge from a previous series. The results, however, are more interesting when broken down by sport.
Out of the 14 times this matchup has occurred in the NBA playoffs, only twice has the team that went to 7 games in the previous series won the next series (1998: CHI vs. UTAH and 1968: BOS vs. LAL). Much more frequently, the team that has swept in the previous series has gone on to win. Whether the reason for its winning is that it generally has had better records, or because they were well-prepared and well-rested, is impossible to say for sure.
The NHL had a similar pattern to the NBA, until 1993; since then, 5 out of 6 teams that went to seven games won the next series against the team that had swept. Most recently, the Carolina Hurricanes defeated the Boston Bruins in the conference semifinals in 2009, even though the Bruins had plenty of time to recuperate.
In the MLB, this type of matchup has only occurred four times, mainly because the LCS is the only 7-game series that occurs before another series, and the LCS has not always been a 7-game series. In all four of these matchups (2012: SF vs. DET, 2007: BOS vs. COL, 2006: STL vs. DET, and 1988: LAD vs. OAK), the team which went to 7 games in the LCS won the World Series. Furthermore, none of these teams has needed more than 5 games to do so.
Although the few data points we have suggest such, concluding that rest is more important in the NBA, whereas momentum is more important in the MLB and NHL is impossible. In truth, both of these components probably impact the outcome of a playoff series, but probably even more important is how good at winning the team is. Out of these 29 series, 21 of them were won by the team with the better winning percentage (or, points for NHL). Being well-rested is helpful — but being good is even more helpful.