As the prestige of winning the Cup grew, so did the need to attract top players, and thus professional teams first became eligible to challenge for the Stanley Cup in 1906. Then in 1908, the Allan Cup was introduced as the trophy for Canada's amateurs, and the Stanley Cup became a symbol of professional hockey supremacy. In 1910, the National Hockey Association (NHA) held its inaugural season and soon emerged as the best professional hockey league in Canada, keeping the Cup for the next four years. In 1914, the Victoria Aristocrats of the Pacific Coast Hockey Association (PCHA) challenged the NHA and Cup champion Toronto Blueshirts. One year later, the NHA and the PCHA began an agreement in which their respective champions would face each other annually for the Stanley Cup, effectively ending the Cup challenge games.