Milton, who spent two years recovering from Tommy John surgery, was 2-1 with a 3.80 ERA in five starts for the Dodgers as their No. 5 starter after signing a minor league deal.
But Milton, who was twice placed on the disabled list this season, underwent the back surgery after suffering a setback in New York last week, according to MLB.com.
While Milton's season may be over, his career could continue, depending on his recovery. Last week he said he had no intention of retiring at the end of the season, according to the Los Angeles Times.