3. Bob Rush 33.5 WAR with the Cubs
I'm bending the rules a bit with this entry since Bob Rush's first two seasons were prior to 1950, however, his best years with the Cubs came after that point so we're rolling with it. Before his solid baseball career, Rush fought for the U.S. Army in World War II where he served under George S. Patton's third army. When he came back from the war, Rush immediately pursued a baseball career and found his way to the Cubs' 40-man roster in 1948.
Rush spent 10 seasons with the Cubs, and in 8 of them, he surpassed the 200-inning mark. Rush also threw 2201.2 innings with the Cubs, more than both Greg Maddux and Zambrano, and made two all-star teams in his tenure. While the Cubs failed to post a winning record for the entirety of Rush's time in Chicago, he proved to be one of the few shining stars on the team and a dependable workhorse in the rotation.