In 1928, at age 16 years, 156 days, he became the youngest tennis player to ever represent the United States in the Davis Cup, and the youngest player to ever compete in a Davis Cup match, both records he still holds.

[need quotation to verify][1] Coen also competed at Wimbledon in 1928 and 29, twice reaching the third round.

In 1930 he won the doubles title with Tilden at the inaugural Italian Open in Milan.

[2] That same year he was a runner-up in singles at the U.S. Men's Clay Court Championships, losing the final in straight sets to Bryan Grant.

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