Hudson left his start Thursday night after two innings due to what he described as discomfort in his right arm.
The 26-year-old is 3-2 with a 2.77 ERA in eight starts this season.
St. Louis added right-handed reliever Nabil Crismatt to take Hudson’s roster spot. Crismatt has a 3.24 ERA in 8 1/3 innings over six appearances this season.
Information from The Associated Press was used in this report.