Cahill, 27, is expected to be used as a reliever but could be stretched out to start and give the Cubs insurance in their rotation. Cahill started his career as an All-Star starter with the Oakland Athletics before he was traded to the Diamondbacks, but he was 3-12 with a 5.61 ERA in 2014 and was dealt to the Braves, who released him after he had a 7.52 ERA in 15 starts in 2015.