It is difficult to compare players from different eras, but it can be done more accurately today thanks to modern statistics.
Walter Johnson was one of the greatest pitchers of all time. He is generally considered the best according to those who saw him pitch as well as by traditional measurements.
Johnson won 417 games from 1907-1927 for a Washington Senators team that finished in the second division 10 times. The Senators won their first pennant in 1924, when Johnson was 36-years-old.
Washington beat the New York Giants in the 1924 World Series and repeated as pennant winners in 1925, but they lost the World Series to the Pittsburgh Pirates.
Johnson pitched primarily during the dead ball era with the exception of his last few seasons.
“The Big Train” had a 2.17 ERA, pitched 5,914.3 innings while allowing only 4,913 hits and hurled 116 shut outs. He struck out 3,509 batters and walked 1,363.
The 116 shut outs graphically illustrate the difference in eras. No pitcher will ever pitch 116 complete games, much less have 116 shut outs.
Roger Clemens is considered one of the top pitchers of the modern era. From 1994 to the present is clearly the most offensive era ever (take that anyone you want). How does Roger Clemens compare to Walter Johnson?
Clemens won 365 games from 1984-2007. He pitched for the Boston Red Sox, Toronto Blue Jays, New York Yankees and Houston Astros. Clemens was on six pennant winners and two world champions.
Clemens had a 3.12 ERA, pitched 4,916.7 innings while allowing only 4,185 hits and pitched 46 shutouts. He struck out 4,672 batters while walking 1,580.
Today’s players are bigger and stronger than those during the first part of the 20th century, but Johnson and Clemens were close physically.
Johnson was six feet tall and weighed 200 lb. Clemens is six-feet-four inches tall and weighs about 205 lb
Now to modern measurements
PITCHER ERA+ WHIP WAR RAR Rrep
Johnson 147 1.061 127.7 1226 3128
Clemens 143 1.173 128.4 1289 3174
ERA+ is ERA adjusted to the ball park.
WHIP is to Walks and Hits compared to Innings Pitched.
WAR is Wins Above Replacement.
RAR is Runs Better Than Replacement
Rrep is Runs expected for Replacement Level
It is extremely close. No statistically significant difference exists between any of the modern measurements, with the exception of WHIP.
There is no doubt that Johnson would have won more games if he had pitched for better teams, but ERA+ confirms that Clemens was just as effective with respect to preventing runs.
Little doubt exists that Roger Clemens holds his own with the all-time greats.