Tebbetts in sole possession of the catcher's position. He responded by posting a .296 batting average, as the Tigers defeated the Cleveland Indians and the New York Yankees in a tight pennant race to clinch the American League title. Tebbetts was held hitless in the 1940 World Series as the Tigers lost to the Cincinnati Reds in a seven-game series. He once again led AL catchers in assists and in baserunners caught stealing. In September, Tebbetts had been charged with assault and battery during a game in Cleveland when a basket of tomatoes was dropped on him by a Cleveland fan. As police held the fan, Tebbetts rushed up and struck him. The charges were later dismissed. He developed a reputation for antagonizing opposing players, constantly hectoring them in an effort to have them make mistakes and give his team an advantage. In 1941, Tebbetts was hitting for a .296 average by mid-season and earned a place as a reserve player for the American League in the 1941 All-Star Game. He led American League catchers in assists for a third consecutive year. Tebbetts was named the starting catcher for the American League in the 1942 All-Star Game. Despite holding a 3-A draft classification because of his mother's dependency, Tebbetts applied for an Army Air Corps commission. He joined the military services in August 1942 and was assigned to recruiting duties in Waco, Texas during the Second World War. Tebbetts honed his managerial skills as a player-manager for the Waco Army Flying School's baseball team. He lost three years of his baseball career to his military service. After his discharge from the military, Tebbetts returned to play for the Tigers in 1946, posting a .243 batting average in 86 games. He was hitting for only a .094 average in May 1947 when he was traded to the Boston Red Sox for catcher Hal Wagner. After the trade, Tebbetts hit for a .299 average for the remainder of the season. There were reports in July 1947 that the Red Sox were considering Tebbetts as a successor to their manager, Joe Cronin. He was hitting for a .286 average at mid-season in 1948 and was named as a reserve catcher for the American League in the 1948 All-Star Game. The Red Sox finished the season in a first place tie with the Cleveland Indians before losing the pennant in a one-game playoff at