From the deadball era, Jesse Tannehill is one of the unsung pitchers from that time.
Bob Friend played most of his career with the Pittsburgh Pirates (1951-63), where he quietly had one of the better decades of the National League's Pitchers.
One of the most underrated players was Brian Giles, who played for three mediocre teams (Cleveland, Pittsburgh, and San Diego) and did not see as much love as he should have.
The younger brother of Baseball Hall of Famer and New York Yankees legend Joe DiMaggio, Dom DiMaggio, was quite the player in his own right.