Cahill, a nine-year veteran, comes back to Oakland — the organization that drafted him — for a second stint hours after the Athletics found out that young starter Jharel Cotton will need Tommy John surgery on his right ulnar collateral ligament and will miss the 2018 season. The 30-year-old Cahill was drafted by the A’s in 2006 and played three seasons with them from 2009-11, posting a 40-35 record with a 3.91 ERA and an 8.4 WAR in 96 starts. His best season was in 2010, when he earned an All-Star appearance and went 18-8 with a 2.97 ERA, a 1.11 WHIP and a 3.9 WAR in 196 2⁄3 innings pitched across 30 starts.
After his 2011 campaign in which threw a career-high 207 2⁄3 innings and made an AL-high 34 starts, Cahill was traded in the offseason to the Diamondbacks, where he spent the next three seasons of his career. He was a starter for the first two seasons before being moved to the bullpen in his third season. In 2015, he got traded to the Braves at the start of the season and has not been the same ever since. Outside of a solid 2016 season as a reliever with the Cubs, Cahill has posted a 0.8 WAR while also bouncing around with the Padres and Royals.
Cahill will try to help boost a rotation that right now only has Kendall Graveman and Sean Manaea as locks. Daniel Mengden, Andrew Triggs, Daniel Gossett and Paul Blackburn are also competing for spots on the staff.