This is unexpected news.
The Pirates did not make an official announcement Monday, but multiple baseball sources indicated a deal with the right-handed pitcher had been reached.
Here's some more information:
I can't find out much about Herrera right now, so I have no idea whether this is a good idea for the Pirates or not. I'm very happy to see them exploring this market, however - the Pirates have neglected international talent for so long that I'm pleasantly shocked by this announcement. Part of the Pirates' interest probably has to do with the potential for Herrera to contribute to the big league team soon. Most international signees take a long time to develop. So this signing may not mean that the Pirates have suddenly decided to start taking other international markets seriously. Here's hoping I'm wrong about that. In the meantime, though, this is an encouraging move, even if Herrera doesn't end up working out.