Born in Utica, Michigan, he was listed as 5 feet 10 inches (1.78 m) tall and 170 pounds (77 kg).

After making his big-league debut in 1955 with Detroit and then struggling through an 0–7 campaign in 1956, Maas put together a 10-win season in 1957.

He also pitched two innings of relief for the Yankees in the 1960 World Series against the Pittsburgh Pirates.

For his career, he compiled a 45–44 record with a 4.19 earned run average and 356 strikeouts in 195 appearances.

Maas died in Mount Clemens, Michigan, at the age of 47 from complications due to arthritis.