Gerald was big at 6'2" and 205lbs, and had great upper body strength. He could dominate in the corners, where he could tie up a guy along the boards with ease. He was also capable of a good open ice hit. He was a good fighter when he did drop the gloves, but that was a rare occurance.
Gerald also had a good package of skills to compliment his physical game. Gerald had tree trunks for legs, which meant a strong skating stride. He had good quickness and mobility. His most attractive finesse quality was his booming hard shot. Gerald was often used on the latter half of a power play because of his shot which often perplexed goalies. He was able to get the shot from the point off quickly too, although it made his shot erratic and therefore often non-threatening. Otherwise Gerald was fairly average in terms of skills. He wasn't a great puck-handler or playmaker. He was more into dumping the puck out his zone as opposed to creating a transitional breakout play. The way to play against Gerald was to forecheck him hard. When under pressure Gerald would make hurried decisions.
Gerald spent three seasons with Lethbridge of the Western Hockey League, where he was named the Broncos best defenseman and MVP of the playoffs. In 1982, he helped Lethbridge to the league's regular season championship. This impressive resume earned him status as a NHL first round draft pick, 16th overall in 1983 by the New York Islanders.
Gerald was solid in parts of 7 seasons on Long Island, but was never able to put all the pieces together to become a dominant NHL backliner. On September 4, 1990, he was traded to the Montreal Canadiens for an aging but stalwart defenseman in Craig Ludwig.
It was hoped that Diduck could develop into a younger version of Ludwig, but Gerald had his troubles in Montreal. Diduck didn't adapt to the Canadiens style of play easily, as it was foreign compared to the way he had played his whole life. As a result he fell out of favor quickly in Montreal and was traded to Vancouver by midseason.
Gerald parts of 5 seasons on Canada's west coast, and really benefited from playing under coach Pat Quinn. Quinn, a former NHL blue line journeyman, had a way of getting the most out of his defensemen, including Diduck. Gerald played very aggressively upon his arrival in Vancouver, and as a result played a more important role on a team than he had at any other point in his NHL career.
Playing aggressively of course leads to injuries. Injuries would slow Diduck down and by late in 1995 he was traded to the Chicago Blackhawks. He finished the season there before signing as a free agent with the Hartford Whalers.
Gerald played an effective role in Hartford for 2 years and another 3 with the Phoenix Coyotes before joining the Canadian National Team in 1999. He signed on with the Toronto Maple Leafs where Pat Quinn was coaching. Diduck did an admirable job for the Leafs who badly needed an experienced, physical blueliner that season.