Knockout system
The knockout system (of English knockout , "knock out" about or "out of action set"), more rarely, single elimination ( English Single elimination unlike Double elimination , see Double knock out ) or knockout ( English Cup System ) , is a form of tournament that is used in sports such as B. tennis or in cup competitions in football is used, whereby the loser of an encounter is eliminated from the tournament. In competitions that are only partially carried out in the knockout system, the corresponding section is also referred to as the knockout phase .
Procedure for a knockout tournament
In each game round two participants meet each other. The winners of the first round games advance to the second round, the losers are eliminated. The winners of the second round matches meet in the third round, while the losers are eliminated again, etc., until two participants remain who fight for the tournament victory in the final .
The knockout system works best when the number of participants is a power of two , i.e. 2, 4, 8, 16, 32 etc .; otherwise some participants receive in the first round bye ( Bye ).
At the same time, the knockout system is the type of tournament that minimizes the number of games and game rounds: with 4 participants you need two rounds, with 8 participants three, with 16 participants four etc. The total number of games results from the number Subscriber −1; so have to determine the winner at z. B. 32 teams 31 games are played. Another advantage of the knockout system is the simple, easily understandable structure.
This form of tournament fulfills most of the requirements for a form of tournament . However, if the pairings are drawn in the first round , it can happen that the best participant meets the second best in the first round, i.e. H. With the simple knockout system, it is not guaranteed that the second best participant will reach second place (provided that the respective favorite wins in every match).
In order to avoid that the favorites meet very early in tournaments with a knockout system, the participants are seeded against each other . In a tournament with 128 participants, the best participant (No. 1) plays against No. 128, No. 2 against 127, etc. in the first round, if the favorites win, so in the second round, player No. 1 against No. 64, No. 2 to No. 63, etc. In the final, the two best face each other.
disadvantage
- Half of the participants drop out in the first round. As a result, weaker players / teams hardly gain tournament experience.
- The advantage that the knockout system minimizes the number of games to be played also results in a disadvantage: the fewer games that are played, the greater the influence of chance, in particular the influence of the draw required before the start of a tournament . The knockout system is therefore only suitable for determining the best player / team, but not the second-best, as the drawing of the best player / team for the second best can meet.
- Tie-breakers must be used to determine a winner in competitions in which there are frequent ties.These are very often controversial (e.g. in football overtime , golden goal , silver goal , penalty shoot-outs , replay games or even throwing one Loses).
Further evaluation
The advantage of a tournament according to the knockout system is that a decision can be made relatively quickly (e.g. compared to a round-robin tournament ). However, a one-time defeat already means elimination from the tournament. Therefore, chance has a very high influence on this tournament format.
The betting favors the favorites, which the other players perceive as unfair. If the playing strengths of the individual participants change only relatively slowly, there will be a large number of identical game pairings in successive tournaments, and that is unsatisfactory for both the organizer and the spectator. In addition, No. 128, which always has to compete against No. 1, would never have a chance to improve.
In tennis tournaments, for example, a mixture of drawing lots and betting is used. In Grand Slam tournaments, only the top 32 players are placed: Player 1 is placed in position 1, player 2 in position 2, players 3 and 4 are drawn to positions 3 and 4, players 5 to 8 are drawn drawn for positions 5 to 8, players 9 to 16 drawn for positions 9 to 16 and players 17 to 32 drawn for positions 17 to 32; all other participants (i.e. players 33 to 128) are drawn.
example
The last three rounds of the French Open 2008 / women singles were played between eight players:
| Quarter finals (VF) | Semi-finals (HF) | Final (F) | |||||||||||||||||
| 13 |  D. Safina
|
4th | 7th | 6th | |||||||||||||||
| 7th | J. Dementjewa
|
6th | 6 5 | 0 | |||||||||||||||
| 13 | D. Safina
|
6th | 6th | ||||||||||||||||
| 4th | S. Kuznetsova
|
3 | 2 | ||||||||||||||||
| 4th | S. Kuznetsova
|
7th | 6th | ||||||||||||||||
 K. Kanepi
|
5 | 2 | |||||||||||||||||
| 13 | D. Safina
|
4th | 3 | ||||||||||||||||
| 2 |  A. Ivanović
|
6th | 6th | ||||||||||||||||
| Q |  C. Suarez-Navarro
|
3 | 2 | ||||||||||||||||
| 3 | J. Jankovic
|
6th | 6th | ||||||||||||||||
| 3 | J. Jankovic
|
4th | 6th | 4th | |||||||||||||||
| 2 | A. Ivanović
|
6th | 3 | 6th | |||||||||||||||
| 10 |  P. Schnyder
|
3 | 2 | ||||||||||||||||
| 2 | A. Ivanović
|
6th | 6th | ||||||||||||||||
Furthermore, it is essential to be able to assess the strength of the individual participants very precisely in advance, which in turn requires very complex and therefore often difficult to understand evaluation methods (e.g. Elo number in chess, world rankings in tennis).
Tournament variants
In a tournament according to the knockout system, the following prizes are awarded: The winner takes first place; the loser of the final takes second place, the losers of the two semi-finals take the two third places. Sometimes the losers of the semi-finals play a “ small final ” among themselves , the game for third place or game for third place .
Places 5 to 8 can also be determined in a similar way: First two losers from the quarter-finals play against each other, then the two winners from these games meet and play for places 5 and 6, while the losers from these games play one game for Place 7 and 8.
In principle, a continuous ranking can be determined by appropriate additional classification games , but this is usually not done; Even holding a game for third place is by no means commonplace everywhere.
Occasionally, the excreted in the first round of participants carry out under a separate knockout tournament, the tournament is Trostrunde or English Consolation mentioned. ( Note : This is a separate tournament and consists of several rounds). Several consolations can also be played: 1st Consolation , 2nd Consolation and Last Chance .
The consolation rounds are sometimes referred to as the hope race , sometimes the winner of that round is allowed to re-enter the main tournament: this essentially leads to the double knock-out format.
In the Bergvall system , after the final there is another knockout round of all participants who were eliminated in direct comparison with the tournament winner. This is to ensure that second place is actually won by the second strongest participant in the tournament. The other placements can then also be played using the same system.
In international soccer tournaments, two games are sometimes played in each round in order to offset the advantages of home law; in this case the points or goals of the two games are added together. In the event of a tie, the away goals rule can be applied.
In order not to bring about the decision through a single game, there are variants in which the one who reaches the next tournament round first reaches a predetermined number of wins. In other words, you redefine the victory needed to advance; this is only achieved after several wins in individual games. So z. B. Best of Five , that the player who has won three times in a maximum of five matches reaches the next tournament round - the loser can then only have a maximum of two wins. This is used, for example, in ice hockey or basketball . In tennis you play best of five or best of three , i. H. the player who wins three or two sets first progresses .
If a discipline allows several participants to compete at the same time , but not for all participants to compete at the same time (e.g. short-distance running , swimming , poker ), the knockout system can be varied as follows: Several preliminary runs are carried out; In each preliminary run, several participants compete against each other in a knockout system, of which a certain number (often half) qualify for the next round.
Well-known competitions that are held in the knockout system are the national soccer cup competitions , such as the German DFB Cup , the Austrian ÖFB Cup or the Swiss Cup . In some competitions (. Eg UEFA Cup , Champions League - qualification , some national cup competition ) do not play all the teams right from the first round, so the number of participants in the early rounds is not a power of two.
Another special variant of the knockout system can be found in card games, namely in price snaps and price flats.
Modifications
In many cases a combination of a knockout system and a round robin tournament is used.