Casewell started his rugby league career at Salford, and went on to play for Leeds, Halifax and Keighley.

[1] Only five rugby league footballers have won "All Six Cups" during their career, they are; Aubrey Casewell (while at Salford and Leeds), Alan Edwards (while at Salford and Bradford Northern), John Etty (while at Oldham and Wakefield Trinity), Edward "Ted" Slevin (while at Wigan and Huddersfield), and Derek Turner (while at Oldham and Wakefield Trinity).

[7] Casewell was one of the players who successfully toured in France with Salford in 1934, during which the Salford team earned the name "Les Diables Rouges", the seventeen players were; Joe Bradbury, Bob Brown, Aubrey Casewell, Paddy Dalton, Bert Day, Cliff Evans, Jack Feetham, George Harris, Barney Hudson, Emlyn Jenkins, Alf Middleton, Sammy Miller, Harold Osbaldestin, Les Pearson, Gus Risman, Billy Watkins and Billy Williams.

Aubrey Casewell played in Leeds' 18-2 victory over Warrington in the 1935–36 Challenge Cup Final during the 1935–36 season at Wembley Stadium, London on Saturday 18 April 1936.

About Aubrey Casewell's time, there was Salford's 2-15 defeat by Warrington in the 1929 Lancashire Cup Final during the 1929–30 season at Central Park, Wigan on Saturday 23 November 1929, the 10-8 victory over Swinton in the 1931 Lancashire Cup Final during the 1931–32 season at The Cliff, Broughton, Salford on Saturday 21 November 1931, the 21-12 victory over Wigan in the 1934 Lancashire Cup Final during the 1934–35 season at Station Road, Swinton on Saturday 20 October 1934, the 15-7 victory over Wigan in the 1935 Lancashire Cup Final during the 1935–36 season at Wilderspool Stadium, Warrington on Saturday 19 October 1935.