Gregg had a great 1910 season in the Pacific Coast League, throwing 14 shutouts. He continued his success in his rookie season with the Indians in 1911, going 23-7 to lead the AL with a .767 winning percentage and a 1.81 ERA.
The powerful lefthander followed with two more 20-win seasons before suffering a sore arm which reduced his effectiveness. Traded to the Red Sox in mid-1914, he never again had a successful ML season, though he was a big winner after he returned to the minors. Younger brother Dave had a one-inning ML pitching career with Cleveland in 1913.