I think this is more indicative of the loss of Zobrist than the addition of Russell. Russell has mostly been great on the defensive end (At the pace he's on, he's gonna lead all 2B in defensive runs saved by a wide margin) and his bat has look good enough before and after he hurt his hand. Descalso on the other hand actually hurts you on both sides. Russell currently has a defensive WAR of 0.07 and is on pace for his worst defensive WAR as a Cub. In fact, his defensive WAR has gotten worse each year he’s been here.