From the past, Al Simmons and Jimmy Foxx were looked at for the possible top slot. From the 70s, there were the three-peat championship members. Rickey Henderson almost made it. But when all the algorithms were done, it was Robert Moses "Lefty" Grove, who was anointed by Notinhalloffame.com as the greatest Athletic of all-time.
Grove was Major League ready years before he debuted. It was a different time back then, as he was a star pitcher for the Baltimore Orioles, not the Major League Baseball Team that you know now, but a team in the International League. Their players were not subject to a draft, and thus for anyone who played there to get a shot at the National League or American League, their contract had to be sold or traded to one of those teams. After years of turning down offers, the Orioles sold Grove's contract to the Philadelphia Athletics for $100,600, a record for the time. It would turn out to be a bargain.
Grove’s rookie season with Philadelphia in 1925 was nothing special (10-12), but his 116 Strikeouts led the American League. The Southpaw would continue to lead the AL in Ks, an honor he would repeat every year to 1931. In 1926, he won his first ERA Title and went on a four-year run leading the league in that category from 1929 to 1932. Wins were also piling up. Grove would lead the AL in Wins four times as an Athletic (1928, 1930, 1931 & 1933), and from 1927 to 1933, he never had a season where he dipped below 20. With Philadelphia, he would also lead the AL in FIP six times, WHIP three times, and SO/BB six times. Grove would win the American League MVP in 1931.
All of this is incredible, but the most crucial part is that Grove was the pitching anchor that won Philadelphia the 1929 and 1930 World Series. He would also take them to the 1931 World Series, though they would lose to the St. Louis Cardinals. He would have a post-season record of 4-2 with a 1.75 ERA.
He would be traded to the Boston Red Sox after the 1933 season, and would win four more ERA Titles and would reach the 300 Win mark.Grove was chosen for the Baseball Hall of Fame in 1947.