The person confirmed the contract to The Associated Press on condition of anonymity Wednesday because it is pending a physical.
Duensing returns to Chicago after signing a one-year deal with the Cubs last winter. The left-hander went 1-1 with a 2.74 ERA in 68 appearances last season.
Duensing, who turns 35 next month, broke into the majors with Minnesota in 2009. He is 43-38 with a 4.01 ERA in nine seasons.
