A round robin is a tournament format in which each team participating plays each other team participating an equal number of times. Examples in League of Legends include the group stages of most Premier Leagues. The Champions Group Stage features a round robin in which each team plays each other team in their group in one Best of 2 match. The NA and EU LCS instead feature each team playing each opponent in 4 best-of-1 matches. Generally, scheduling is done such that each team plays an equal number of games on the blue side and the purple side, or a number of games that differs by no more than 1 (if each team will play an odd number of games). The number of games in a round robin with n teams is equal to n(n-1)/2, multiplied by the number of times each team plays each other team.
The primary advantages of a Round Robin tournament are the large number of games for players and spectators, the increased chance that a team that can perform consistently will win, and the fact that all teams in the tournament, even those far from the top, receive a fairly accurate exact ranking (compared to single elimination and elimination-consolation tournaments).
Example structure of Round Robin Tournaments
In a simple 4 team round robin with 2 games played simultaneously in each round, the schedule might look like this, with the team on the blue side listed first.
|Round||Match one||Match two|
|Round 1||Team A v. Team D||Team B v. Team C|
|Round 2||Team C v. Team A||Team D v. Team B|
|Round 3||Team A v. Team B||Team C v. Team D|
For a 6 team round robin, the schedule increases in complexity, looking something like this.
|Round||Match one||Match two||Match three|
|Round 1||Team B v. Team A||Team C v. Team F||Team D v. Team E|
|Round 2||Team C v. Team D||Team F v. Team A||Team B v. Team E|
|Round 3||Team F v. Team D||Team B v. Team C||Team A v. Team E|
|Round 4||Team D v. Team A||Team E v. Team C||Team F v. Team B|
|Round 5||Team E v. Team F||Team A v. Team C||Team D v. Team B|
Tiebreaking Methods in Round Robin Tournaments
One of the most common means of breaking a tie between teams with the same record in a round robin tournament is to simply have those teams play a tiebreaking game (or games, if more than two teams are tied). This method or the drawing of lots are often used if other methods of tiebreaking fail, and is sometimes used as the only tiebreaker permitted.
Strength of Victory
Used frequently as the first means of breaking a tie is the strength of victory method, in which the head to head record between tied teams determines which of the teams receives the higher finish. If more than 2 teams are tied, either this method may be ignored, or the total record among all tied teams may be considered.
Originating in chess, the Neustadtl score is a form of tiebreaking score found by adding up the number of wins that a given team defeated, under the belief that a win against a strong team ought to be more rewarded than a win against a weaker team. In tiebreaking for first place, this usually has the same result as Strength of Victory, but it may produce a different result when breaking ties among teams lower in the standings. For example, in the 2013 International Wildcard Tournament, Lyon Gaming would have advanced over Dark Passage in 4th place if the Neustadtl score were used instead of Strength of Victory, but paiN Gaming would still have held first place over GamingGear.eu in the Group Stage.
Time of Victory
Now rarely used in competitive League of Legends but once common, this system can be used to break ties either in favor of the team who played shorter games in their victories, longer games in their defeats, or some combination of the two.
Spiral of Death
The largest problem a tournament organizer may face is the possibility of a ‘Spiral of Death’, a situation in which 3 or more teams have identical records in a tournament and identical records against each other, such as the top 3 teams in an 8 team round robin all finishing 6-1 with 1-1 records against each other. If a tiebreaker round robin is played among the three tied teams to break the tie, the same result may perpetuate itself indefinitely, especially if the teams' playstyles contribute to each team having a distinct advantage against one opponent but not the other. This tie can generally only be broken by methods often considered unfair, such as time of victory, or even drawing of lots, especially if time is a constraint.