Red Sox sign Doug Mathis

The Red Sox signed about 11 minor league free agents this past week, including some former familiar names such as Brandon Duckworth, Carlos Silva, and Tony Pena Jr. However, the one I wanted to focus on former Ranger pitcher Doug Mathis. He pitched for the Samsung Lions in the KBO in 2011 and had a 2 PE (with almost as many walks as strikeouts). When this is converted to the MLB, this a horrendous 4.54 PE. So it doesn't seem that he is ready for MLB success according to his KBO statistics. In his Major League career, his PE is 5.015 with a -.1 WAR in 87.1 innings. So he actually performed slightly better in the KBO than expected. In his MLB career, he has a FIP - of 121, SIERA of 4.79, and 5.625 Adjusted PE. Obviously these numbers are horrible. His AAA numbers are pretty bad too, with a 2.88 PE in the PCL, which translates to a 4.31 PE in MLB. So according to his AAA numbers, he has underperformed in the Majors, but nothing could really be expected of him anyway. I am not sure what the Red Sox see in Mathis, there isn't much there, and several different metrics show this.