Variations of the Shaughnessy system also exist, such as in the promotion playoffs held by League 1 of the British rugby league. When a playoff of this type involves the top four teams, it is sometimes known as the Shaughnessy playoff system, after Frank Shaughnessy, who first developed it for the International League of minor league baseball. In most tennis tournaments, the players are seeded against each other, and the winner of each match continues to the next round, all the way to the final. Single-elimination tournaments are often used in individual sports like tennis. A single-elimination ('knockout') playoff pits the participants in one-game matches, with the loser being dropped from the competition.