There are two things I feel should be common knowledge by now about relief pitchers.

1. Relief pitchers are very volatile.

2. ERA is a horrible stat to evaluate relievers.

The Pittsburgh Pirates have had success finding strong relievers at low costs because they've ignored short-term struggles, and have looked past a poor ERA to see potential with advanced metrics. Meanwhile, other teams give out long-term deals to relievers, paying them millions of dollars, and mostly for the ERA.

Eventually other teams are going to get it, but it doesn't look like that has happened yet.

The trade between the Angels and the Pirates looks like the Mark Melancon trade all over again. The Pirates sent Jason Grilli for Ernesto Frieri. They dealt an aging reliever who looks like he's on a rapid ...

To continue reading the rest of this article, subscribe to Pirates Prospects. Subscribers get access to every article on the site, along with all of our exclusive live coverage of the Pirates' minor league system, all for a very low monthly or yearly rate.

If you're already a member, you can log in below. If you think you're receiving this message in error, please e-mail tim@piratesprospects.com.