Career
In 1920 he reached the final of the mixed doubles competition at the United States. National Championships (now United States Open) together with Molla Bjurstedt Mallory. They lost the final to Hazel Hotchkiss Wightman and Wallace F. Johnson in straight sets. His best singles performance in a Grand Slam tournament was reaching the quarterfinal of the United States. National Championships in 1917, 1918 and 1921.
In September 1913 Biddle reached the final of the Montreux Autumn Meeting in Switzerland but was defeated by Anthony Wilding in three straight sets.
In March 1920 he was runner-up at the Florida Tennis Championships, losing in the final in straight sets to Ichiya Kumagae. Mixed doubles
= Runners-up (1) =.
