Despite the fact that he hit a home run in his first major league at-bat on September 8 of his debut season, Kerr was known mostly as a slick fielder with a very light bat.

He led National League shortstops in assists, putouts, and double plays in 1945, and achieved a top .982 fielding average in 1946.

He was promoted to Jersey City of the International League, where he'd spent the next two seasons before joining the Giants as the backup to Billy Jurges.

Kerr remained the regular shortstop for the Giants until he was traded to the Boston Braves ahead of the 1950 season, along with Willard Marshall and Sid Gordon, for Alvin Dark and Eddie Stanky.

In 1953, he returned to the Braves, who by this time had relocated to Milwaukee and was assigned to the Toledo Sox, their top minor league affiliate.