Gaetz was drafted to the National Hockey League by the Minnesota North Stars 40th overall in the 1988 NHL Entry Draft, as a protection for Mike Modano, their highly touted first pick that year. Gaetz only played 17 games for the North Stars, spanned over two seasons, before being selected by the San Jose Sharks in the 1991 NHL Expansion Draft. His fists made him a fan favourite in the Golden State, but his stay there didn't last very long either.
On April 2nd 1992, Gaetz was thrown from the passenger seat of a Camaro driven by his friend, who was driving under the influence of alcohol, after he lost control of the car on an off-ramp at the speed of 80 mph. Gaetz arrived at the Peninsula Hospital with back and facial injuries, and remained semicomatose for eight days; doctors feared for his life. Injured to the brain stem, Gaetz awoke with his left side partially paralyzed and no memory from the accident. Over the next two months, rehab followed, in order to help him regain control of movement and speech. He confounded the doctors by resuming skating during that summer. He was released from the hospital. Several months later, he was arrested for drunk driving. Sharks GM Dean Lombardi gave up on his case and traded him to the Edmonton Oilers for future considerations. This trade marked the last time he would play in the NHL. All in all, Gaetz played only 65 NHL games, scoring a meager six goals and adding 8 assists. He however accumulated 412 penalty minutes and established a Sharks' franchise record for the most penalty minutes in a season (326) in 1991-92.
After his NHL career, Gaetz played in various minor leagues for 13 years. He also played roller hockey for one season in 1994. His career ended on March 13th 2005 when he was suspended from his team, the Thetford Mines Prolab of the Ligue Nord-Américaine de Hockey. In a game against the Verdun Dragons on that day, Gaetz didn't take a shift during neither the first nor the second period. In the second intermission, he changed out of his jersey and skates and went to the concession stand to buy a hamburger, and "promptly ate it". The Prolab considered this disrespectful to the players and promptly suspended him for the remainder of the season.