Mitterwald backed up Johnny Roseboro on the Twins 1969 division-winning team and became the primary catcher in 1970 when they repeated. He hit .222 with 15 HR and 46 RBI in 1970 and hit .500 in Minnesota’s losing effort in the LCS. He played the most in 1973, catching 122 games and reaching career highs of 16 HR, 64 RBI, 50 runs, and .259. He was traded to the Cubs for Randy Hundley after the season and spent four years backing up Steve Swisher. Mitterwald hit three homers in an April 17, 1974 game against the Pirates. After Swisher was traded, Mitterwald was the Cubs’ number-one catcher in 1978, his last season.