WASHINGTON -- For the second time in the past three days, the Pirates have added a pitcher to the club's 40-man roster in an effort to bolster the organization's depth.

On Monday, the Pirates claimed right-handed reliever Steven Jackson off waivers from the Yankees. Jackson, who has been assigned to Triple-A Indianapolis, allowed three earned runs, three walks and recorded eight strikeouts in 14 1/3 innings with the Yankees' Triple-A affiliate before being designated for assignment on May 8.

He was designated for assignment in order to clear a space on New York's 40-man roster for catcher Kevin Cash.

Jackson, 27, has never pitched above Triple-A, though he spent most of the 2007 and '08 seasons at that level. A former 10th-round Draft pick, Jackson has pitched both as a starter and as a reliever in the Minors. One of his seven appearances this season came as a starter.

General manager Neal Huntington said that Jackson piqued management's interest because of his ability to throw strikes with an average three-pitch mix. Jackson also has three option years remaining, which gives the Pirates plenty of flexibility with his developmental process.

"We feel he can help a Major League club in middle relief with potential upside for more," Huntington added.

In order to clear space on the roster for Jackson, the Pirates granted right-handed starter Jimmy Barthmaier his unconditional release. Barthmaier just underwent Tommy John surgery and was slated to be out for the next 12-18 months. He hurt his elbow in his first start of the season.

The Pirates had the option of placing Barthmaier on the 60-day disabled list, but Barthmaier's circumstances may not have allowed the righty to pitch for Pittsburgh even after he recovered.

Barthmaier is out of options, having used his last option year this season. As a result, the Pirates would have had to keep Barthmaier on the Major League disabled list until he was healthy next year, which would have been at the earliest in May. Barthmaier would have then been given a 30-day rehab window, after which the Pirates would have had to carry him on the Major League roster or risk losing him to another team.

With Barthmaier still needing to reach additional developmental goals in addition to coming back from the injury, it's unlikely that he would have been deemed Major League-ready after those 30 days. As a result, the Pirates made the decision not to invest a season's worth of resources in Barthmaier with the risk of losing him after doing so.