Detroit's Zimmermann, Stewart have core muscle surgery
The Tigers said the operations took place in Philadelphia and were performed by Dr. William Meyers.
Zimmermann went 7-8 with a 4.52 ERA in 25 starts this season.
Stewart, one of Detroit's top prospects, made his major league debut this year. He played 17 games for the Tigers, hitting .267 with two home runs.
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Updated October 11, 2018