"A hard-throwing pitcher, I didn't appear in the Majors until I was 27 years old, and my first full year I was 28. I struck out a lot of people, but also walked a lot of people, frustrating my managers and coaches with unfulfilled potential. I didn't post an ERA better than league average until I was 31, but then I had a run of success, although being used as a swingman by a contending team. At age 35, I won 19 games, and made the All-Star team, but in so doing I burned out my arm. I got hurt the next year, missed all of my age 37 season, then had a poor comeback at age 38. A handful of poor innings at 39 ended my career. Who am I?"