Reportedly a minimally displaced fracture in the fourth metacarpal in the left hand.

From the Trib:

Alfonso Soriano will be in a splint for three weeks with a broken bone in his left hand, and is expected to miss approximately six weeks of action.

X-rays of the hand taken at Northwestern Memorial hospital revealed a minimally displaced fracture of the left fourth metacarpal, located just under the fourth finger on his left hand.

Soriano was hit in the left hand by a pitch from Braves starter Jeff Bennett and was removed from the game for a pinch-runner in the second inning..

The Cubs will call up outfielder Micah Hoffpauir from Triple-A Iowa on Thursday to take Soriano’s place on the roster. 

More updates later.