Francisco Liriano says he broke his non-pitching arm when he was trying to surprise his kids at Christmas:

Francisco Liriano said he broke his arm when he slammed it against a door, trying to startle his kids Christmas Day. #Pirates

Liriano also says he'll be better in four weeks, which I think would make it very likely that he'll start the season on the DL -- it'll be hard for him to get his arm strength up to par if he's not pitching until mid-March.

Also, here's a picture of Liriano throwing with a brace Sunday in Bradenton.