Through yesterday's game, he had 7.3 WAR in 85 games. I found all the seasons with 7.3 or more WAR from 1901-1912 at Baseball Reference. Then ranked them by WAR per game. Trout is 2nd only to Ruth's 1923 season. Then I found the top 200 seasons in WAR from 1871-1900 and ranked them by WAR per game. The table below shows the top 10 from the two searches.