Potter was the only ML pitcher ever suspended for throwing a spitball. He had a habit of wetting his fingers before picking up the resin bag. On July 20, 1944, pitching for the Browns against the Yankees, he was warned by umpire Cal Hubbard, then on the next occasion thrown out of the game. He was suspended for ten days, although he always denied throwing a spitter. The incident probably cost him a 20-win season; he was 19-7 for the pennant-winning Browns. He gave up only one earned run in two World Series starts, but six Browns errors left him with an 0-1 record.
In 1948, while a reliever with the Athletics, he got into a clubhouse argument with Connie Mack and demanded his release. When it was granted, he signed for a bonus with the Braves and went 5-2 to help them win the NL pennant.
Potter relied on the screwball and slider. With the 1938-40 Athletics he compiled a poor 19-38 mark, and in 1941 when an old knee injury failed to respond to surgery, he was sold to the Red Sox. Returned to the minors, in 1943 he was drafted by the Browns.