Detroit will receive pitching prospects Alex Lange and Paul Richan in the deal, per The Athletic's Patrick Mooney.
Castellanos is slashing .273/.328/.462 in 2019. He leads the American League with 37 doubles while adding 11 homers. Castellanos hit 23 home runs in 2018, smacking 26 homers along with 101 RBIs in 2017.
The 2010 first-round pick is a career .274 hitter. He's totaled 104 homers in seven MLB seasons.
The Cubs enter Wednesday night second in the National League Central at 56–50. They are seeking their third division title in the last four seasons.