The list of 19 Harvard alumni (not necessarily graduates) who played in the big leagues doesn't have a lot of names that I recognize. I see Eddie Grant, the longtime Giant infielder who was first major leaguer killed in WWI, longtime umpire Jocko Conlon, and Pete Varney, who caught the two-point conversion pass that tied Yale in 1968.
https://www.baseball-almanac.com/college/harvard_university_baseball_players.shtml