There would be nothing shocking to baseball fans to hear that there was a year when Babe Ruth lead the Majors in Home Runs and Slugging %, and that his team won the World Series that year. This happened quite often. What most of us would not guess is that this also happened before his Yankees days, when he was in the transitional period between pitcher and hitter. In 1918, Ruth and the Boston Red Sox won the pennant and World Series in a war-shortened season that ended in September.
While Ty Cobb and George Sisler had higher positional fWAR scores, I would argue that Ruth was the MVP of the American League that year. In addition to leading all of MLB in homers and SLG (with a 189 wRC+), he also had the 9th best ERA of all AL pitchers with at least 150 IP. He had a 5.2 fWAR as a hitter, and a 1.6 fWAR as a pitcher. But putting aside WAR, imagine the incredible value of one player being able to give you top-5 hitting and top-10 pitching. We have nothing in modern times with which to compare.
In 1918, the enormous Hippo Vaughn (he was 6’4″, 215 lbs.) lead all pitchers in the National League in IP, ERA, FIP, WHIP and K’s. With a 1.74 ERA, he lead the Cubs to the World Series (only to lose to Ruth’s Red Sox). Even in a shortened season, Vaughn clocked 290.1 innings pitched, with 27 complete games and 8 shutouts.
Among NL position players, the highest wRC+ was 152, and the highest fWAR was 5.5. Neither of those numbers is particularly award-worthy, and no one player seemed to excel in more than one area (either hitting or fielding, but not both). Vaughn seemed particularly dominant in a pitcher-dominated season.