He formed a doubles team with Allan Kendall Jr. and won the NSW, Victorian and Australian Junior titles.

[9][10][11] In 1953, he won the doubles title at the U.S. Championships with Mervyn Rose, defeating Gardnar Mulloy and Bill Talbert in the final that lasted 77 minutes.

In 1953, he played the doubles match with Lew Hoad in the challenge round against the US and lost to Vic Seixas and Tony Trabert.

[15][16][17] In March 1952 Hartwig won the South Australian Championships at Milton Courts, Adelaide defeating Ken McGregor in the semifinal and Rose in the final in a close five-set match.

Australian tennis player and coach Harry Hopman characterized Hartwig as a great stylist.