1968

Burwash lost in the first round of the U.S.T.A. National amateur championship of 1968, played at the Longwood Cricket Club in early August to Dick Stockton. Three weeks later at the inaugural U.S. Open, Burwash lost his opening main draw match to Bob Lutz.

1969

Burwash won his only professional tour match in the opening round of the 1969 Cincinnati Outdoor, defeating American Roy Sprengelmeyer. Burwash then lost in the second round, to No. 9 seed Željko Franulović. Burwash also played in the doubles main draw in Cincinnati where, with partner Stanley Pasarell, he lost in the first round.

The following month, Burwash played in the Canadian Open for the first time where after a first round bye, he lost to Brian Fairlie. In doubles, he reached the second round partnering American Rudy Hernando.

Two weeks later, at his second U.S. Open, Burwash was beaten by Jim Osborne. Again partnering Hernando in doubles, the pair lost their opening match by exactly the same score, to the British pair of Mark Cox and Peter Curtis.

In October at the Barcelona Outdoor, Burwash lost in straight sets to Australian Allan Stone in singles. In doubles, he also lost in the first round, in 5 sets.

1970

In 1970, Burwash played in his only Davis Cup tie for Canada, winning a dead rubber against Caribbean Davis Cup team player Leo Rolle. Canada won the North and Central America Semi-final tie, played in June, 5–0.

In his only tournament main draw singles action for the year, at the U.S. Clay Court Championships in July, Burwash lost in the first round, to Terry Addison. He played one main draw in doubles, at the U.S. Open, again with partner Rudy Hernando, and lost by default to Roy Emerson and Rod Laver.

1971

Burwash competed in main draws at two major events, the Canadian Open and the U.S. Open. In Montreal, he lost to Ismail El Shafei in singles, and partnering compatriot Ken Binns, lost to Bob Lutz and Charlie Pasarell in doubles. At Forest Hills, he was beaten by Milan Holeček.

Burwash won the Canadian National Championships singles (closed) defeating Jim Boyce in the final and thereby gaining the Canadian No. 1 ranking for that year.^[3] Burwash won the third annual Omnium de Tennis Labatt du Québec or Quebec Open played at the Club de Tennis des Loisirs de Granby defeating Rudy Hernando of Detroit in the final in three sets.^[4]

1972

Burwash participated in the main draw in both singles and doubles at the Columbus Outdoor, losing to Charles Owens. In doubles he also lost in the first round, partnering Ian Fletcher. A week later at the U.S. Clay Court Championships, Burwash lost to Toshiro Sakai. In doubles, he and partner William Higgins lost to Jim Delaney and James Chico Hagey. The following week at the Canadian Open, his last appearance there in a main draw, Burwash lost to Jaime Fillol after a bye in the first round.

1973

Burwash was entered in the main draw of two grand prix events. At the Calgary Indoor, held in February, he lost in the first round to Nicholas Kalogeropoulos. In doubles Burwash partnered Franklin Robbins and lost in the first round as well. In August, Burwash was set to play John Newcombe in the first round of the Louisville Outdoor but defaulted.

1974

Burwash lost by default to Bob Giltinan in the first round of the Calgary Indoor in what would be his last tour result. The computer rankings having been introduced only in September 1973, Burwash received his highest singles ranking in June 1974, when he was ranked World No. 240. He never earned a doubles ranking, as they were not kept until 1978.^[5]