Lefty Grove (1925-1933)
Lefty Grove did not make his major league debut until he was 25 years old. That was because his minor league team, the Baltimore Orioles, refused to part ways with a pitcher who was a once in a generation talent.
When they finally sold him to the Philadelphia Athletics for the princely sum of $100,000, he struggled initially. While he led the American League in strikeouts, Grove had issues with bouts of wildness. However, he quickly adjusted, leading the league in ERA and strikeouts in his second year.
By the time he was traded from the Athletics, Grove had established himself as one of the best pitchers in the game. He was the 1931 AL MVP, winning the second of his Triple Crowns. Grove led the league in ERA five times, and was the strikeout leader in each of his first seven seasons. While he did not have as many strikeouts later in his career, Grove was still a brilliant pitcher into his late 30s.
Although Grove spent just nine years with the Athletics, he had quite the impressive run. Overall, he posted a 195-79 record, with a 2.88 ERA and a 1.250 WHiP. In his 2450.1 innings in Philadelphia, he struck out 1523 batters while issuing 740 walks. Grove even added 50 saves during that time.
Had he reached the majors earlier, Lefty Grove may have been considered one of the greatest pitchers of all time. Even with that delayed start, he was one of the best pitchers of his era, and in the history of the Athletics.