The Cubs announced Tuesday that they have signed the right-handed reliever to a major league contract but have put him on the 60-day disabled list as he recovers from Tommy John surgery.
"You can never have enough pitching depth,'' Cubs manager Joe Maddon said. "I had no idea this was going to happen today. When I saw that, I was obviously very pleased.''
Maddon would not speculate on when Nathan would pitch for the Cubs.
"I have no idea,'' Maddon said. "I have not spoken with him.''
The deal, announced Tuesday, is for the major league minimum $507,500 this year and gives the Cubs a $1.5 million option for next season. He has $100,000 in games bonuses for this year, $800,000 in games finished bonuses and $1.5 million in roster bonuses. In 2017, the bonus opportunities are $100,000 for games, $1.5 million for games finished and $2.5 million based on roster time.
If Nathan pitches in at least 30 games this year, has at least 75 days on the active major league roster and a medical exam determines he finishes the season uninjured, the option price would increase to $1.75 million and there would be a $125,000 buyout if it is declined. If he also has 30 games finished this year, it would become a $2 million mutual option and include a $250,000 buyout if the club declines.
Nathan, 41, is a six-time All-Star with 377 career saves, good for eighth in MLB history. He had 35 saves in 2014 for Detroit, but his ERA soared to 4.81. He pitched on Opening Day in 2015 and got a save but did not appear in another game. He underwent Tommy John surgery that April.
The Cubs have had some trouble bridging the gap between a league-best starting rotation and closer Hector Rondon. Pedro Strop has been fairly consistent in the eighth inning, but Justin Grimm sports a 4.85 ERA, Travis Wood is at 4.66, Neil Ramirez 4.91 and Clayton Richard 6.35.
Nathan had 260 saves and a 2.16 ERA in seven seasons with the Minnesota Twins from 2004-11. He signed as a free agent with the Texas Rangers in 2011 and had 80 saves in two seasons. He also pitched for the Giants in his 15-year career.
The Tigers declined their $10 million team option on Nathan this offseason.
The Associated Press contributed to this report.