By 1938, Ross believed the Bruins needed an overhaul, and as part of it asked Clapper to move back to defence. Paired with perennial superstar Eddie Shore on the backline, the move proved highly successful, and Clapper was named a First Team NHL All-Star on defence in 1939, 1940 and 1941, leading the Bruins to Stanley Cup victories in 1939 and 1941.