Hallett, a native of Toledo, Ohio, made his big-league debut on September 13, 1940 at the age of 25 for the White Sox, wearing #28.

On December 9, 1941, Hallett was traded from the White Sox with Mike Kreevich to the Philadelphia Athletics for Wally Moses.

He went from the A's to the Toronto Maple Leafs in the International League in the spring of 1942 before being traded in September to the Pirates.

In 1943, with his number changed to 40, he posted a tiny 1.70 ERA in 47 innings of work, but still had a losing record of 1 and 2.

[2] Hallett came back after his time in the military and posted a solid 3.29 ERA in 115 innings of work for the Pirates in 1946.