The Cubs' primary goal this offseason was to add more depth with the pitching staff, and they have already agreed to terms with free agent John Lackey, whose deal will be finalized once he completes a physical, which is expected to be done this week.
Cahill, 27, was a starter with the Athletics, D-backs and Braves, but was released by Atlanta last June, and again by the Dodgers last August.
He signed a Minor League deal with the Cubs on Aug. 19, and after a stint at Triple-A Iowa, he made 11 relief appearances for the Cubs, giving up four runs on eight hits over 17 innings. In six postseason appearances, he made six appearances.
An American League All-Star in 2010, Cahill has a career 4.16 ERA in 173 starts, and a 3.53 ERA in 39 relief outings.
In the 2015 National League Division Series against the Cardinals, Cahill picked up the win in relief in Game 4.
"Bottom line right here, he's throwing a lot of strikes," Cubs catcher Miguel Montero -- a former teammate of Cahill's in Arizona -- said at the time. "In Arizona, he was really wild. He was spiking fastballs, he was probably getting ahead really quick on the hitters, and then he just ended up walking them.
"He was a pretty good acquisition by the organization in late August," Montero said. "I was really happy when we signed him. I actually remember texting somebody in the front office saying, 'Hey, that was a great sign.'"
After he was released by the Dodgers, Cahill was pitching batting practice at Triple-A, waiting for a job. When he joined the Cubs in the summer, he wasn't sure what role he'd have. Manager Joe Maddon had heard the right-hander was changing his delivery and told Cahill to be himself. It worked, as Cahill compiled a 1.76 ERA in nine appearances in September.