To see what I have already done, click on Part 1 and Part 2 and Part 3. So far, I have not found that in his late thirties or early 40s that Clemens had an unprecedented improvement. Early 40s was good, but not the best. Late 30s was not good, with many pitchers doing better than he did. I have looked at many stats, sometimes adjusting for park effects and league averages. Pitchers that show more improvement than Clemens include Nolan Ryan and Dennis Martinez.
In this post, I simply show that both Ted Lyons and Cy Young also either showed significant improvement late in their careers or did unusually well. In the graphs below (the last thing), the pink line is strikeout-to-walk ratio (not adjusted for the league average. The blue line is ERA+ (from Baseball Reference). It adjusts ERA for the league average and park effects. A 120 means the pitcher is 20% better than average. But I divided the ERA+'s for each guy by 100 to fit in the graph. So 120 would become1.20.
To give you an idea of what I found, when Cy Young was 39, his ERA+ was 86. When he was 40, it was 129. So it went up 50%. When he was 41, it was 194. so it went up 50% again. When Clemens was 40, his ERA+ was 112. When he was 41, it was 146. So it went up 30%. When he was 42, it was 226. So it went up 55%. Those two events look very similar. Just one year difference in age. Cy improved even more over the two years than Clemens. Young also had a big spike up in ERA+ at 34.
Then there is Ted Lyons. Here are his ERA+’s from age 32 on
He pitched 180 innings at age 41 in 1942. Even in 1942, most of the good hitters had still not joined the military (Williams and DiMaggio, for example were still there). Lyons had a career ERA+ of 118. So in his late 30s and early 40s, he was generally pitching well above his career average. My point is that late career improvements are not totally unheard of (although not common). Notice his strikeout-to-walk ratio more than doubled late in his career. I am not sure what Clemens has done in terms of an unusual age profile is much different than Lyons or Young. Now the graphs. Age is on the horizontal axis and strikeout-to-walk ratio & ERA+ are on the vertical.