On Saturday, Mitch Harris became the first Naval Academy graduate since 1921 to play in a Major League Baseball game, according to the Baseball Hall of Fame and the academy itself. Many of the stories noting Harris’ achievement, or his initial call-up to the St. Louis Cardinals from the minors, gave a passing mention to his lone USNA predecessor: Nemo Gaines, who pitched in four games for the Washington Senators. Like Harris, Gaines pitched in relief. Unlike Harris, his time in the majors didn’t come after his time in active service: Gaines secured what amounted to extended leave to pitch in the…