It was first presented to the playoff champion of the NHL ( replacing the O'Brien Trophy ) who then went on to face the Western Hockey League ( WHL ) champion for the Stanley Cup . It was then awarded to the NHL playoff champion in 1925 â `` 26 and 1926 â `` 27 , ( supplementing the O'Brien Cup ) before that team would go on to face the Western Hockey League ( WHL ) champion for the Stanley Cup . After the demise of the WHL , however , the Stanley Cup was awarded exclusively to the NHL playoff champion , and the Wales Trophy was given to the regular season champion .