In a move that can only be described as "inexplicable," the Cubs have signed 41-year-old reliever Joe Nathan to a major-league contract, according to a press release from the team:
Nathan has been placed on the 60-day disabled list as he continues his recovery from Tommy John surgery that took place in April, 2015.
Nathan, thus, is not taking up a 40-man roster spot and there's still one open spot on that roster.
Recovery from TJS can last from a year to a year and a half, so I'd presume Nathan wouldn't be anywhere close to pitching until after the All-Star break. He pitched to just one hitter for the Tigers in 2015 and wasn't very good for them in 2014 (4.81 ERA, 1.534 WHIP, seven blown saves).
I suppose Nathan could wind up being bullpen depth later in the season; he's certainly not going to replace Hector Rondon at closer, nor Pedro Strop in the primary relief role. "Terms of the deal were not disclosed," according to the release, but you'd have to think it's not for very much guaranteed money and includes incentives.
Low-risk, I suppose, but since Nathan hasn't had a good year in the major leagues since 2013 and is almost 42 years old, I wouldn't think there's any huge reward here either.