McCaskill was born in Kapuskasing, Ontario, where his father Ted McCaskill played for the local senior league hockey team. As a child, McCaskill moved several times due to his father’s professional hockey career. He lived in Nashville, Memphis, Vancouver, Phoenix, Newport Beach and Huntington Beach. McCaskill’s father retired from hockey in 1975 and his family settled in Paradise Valley, Arizona. McCaskill attended Edison High School in Huntington Beach his Freshman year before being accepted at Trinity-Pawling School in Pawling, New York. He move to the boarding school mainly to pursue his hockey career, but continued to play baseball while there. During his senior year, McCaskill had an 8–0 record with an 0.97 ERA and 97 strikeouts, scored 26 goals and 22 assists in 17 hockey games, and was the varsity soccer team’s leading goal-scorer. He turned down a baseball scholarship to Arizona State University so that he could pursue both hockey and baseball at the University of Vermont. McCaskill played center and right wing for the University of Vermont from 1979 to 1983. In 1982, McCaskill was a finalist for the Hobey Baker Award and named to that season’s NCAA East All-America First Team and the ECAC All-Star First Team. He was the team captain during the 1982–83 season, and won the Cunningham Award as the Most Valuable Player on the Catamounts. McCaskill was drafted in the fourth round (64th overall) by the Winnipeg Jets in the 1981 NHL Entry Draft. He played only one season of professional hockey for the Sherbrooke Jets, a Jets farm team. McCaskill dressed for one game with the Winnipeg Jets of the NHL but did not play in the game. During the 1983–84 season, he scored 10 goals and added 12 assists for 22 points. He retired from professional hockey after the one season to focus on his professional baseball career. Inducted into the Vermont Sports Hall of Fame in 2015 for his achievement in hockey and baseball. All-ECAC Hockey First Team, 1981-1982. AHCA East All-American, 1981-1982.