The Pirates also elected to protect right-hander Ramon Aguero. Though his name is not as well recognized as the other three, Aguero's upside was too intriguing to leave him available to be taken by another club.
Aguero's performance slipped in 2008, but he showed an impressive rebound in '09. Aguero, who was signed as a non-drafted free agent in July '05, went 2-4 with a 3.86 ERA in 39 games (three starts) last year in low-A West Virginia, high-A Lynchburg and Double-A Altoona.
"He's a potential back-end reliever," Huntington said. "He has a big arm and sinker. He's fearless and throws strikes."
In addition to protecting these four Minor League players, the Pirates made three other roster additions. Jose Ascanio and Evan Meek were both reinstated from the 60-day disabled list, and right-hander Chris Jakubauskas was claimed off waivers from Seattle.
Jakubauskas, 30, made 35 appearances (eight starts) for the Mariners in 2009 and finished 6-7 with a 5.32 ERA. Pittsburgh plans to give Jakubauskas the opportunity to compete for a spot in next year's bullpen.
In order to clear a roster spot for Jakubauskas, however, the Pirates made the somewhat surprising decision to designate right-hander Jeff Karstens for assignment.
Huntington explained the reasoning for the move as simply to give the club more bullpen flexibility. Karstens was going to enter '10 with no options remaining. Jakubauskas, on the other hand, does have options left, meaning that if he doesn't make the team out of Spring Training, the Pirates can easily send him to Triple-A to start the season.
"We feel like he and Jeff can fill a similar role on the club, but Chris has the options remaining," Huntington said. "It's a calculated risk."
The Pirates have 10 days to trade, release or outright Karstens to the Minors -- if he clears waivers. Huntington said the club will explore the trade market for the right-hander.
Pittsburgh designated two other players -- catcher Robinzon Diaz and lefty Justin Thomas -- in order to finish clearing roster space for Friday's additions.
Though Diaz did fare pretty well offensively while he was with the big league club during parts of the '09 season, he remained behind Ryan Doumit and Jason Jaramillo on the Pirates' depth chart going into next year. And like Karstens, Diaz was out of options, meaning that he would have been placed on waivers next spring if he hadn't made the Opening Day roster.
The Pirates have 10 days to trade or release Diaz, who could then become a Minor League free agent. Based on Diaz's reaction to spending the year behind Doumit and Jaramillo, the Pirates do not anticipate him showing interest in returning.
"We welcome him back, but the reality is that he was frustrated at times this year as guys passed him by," Huntington said. "It's our anticipation that he would sign elsewhere."
Without Diaz, catcher Erik Kratz moves up to third on the Major League catching depth chart. Huntington did add, though, that the Pirates will continue to explore free agents to see if the team can improve that depth.
"We feel comfortable with Doumit, Jaramillo and Kratz as our emergency third guy," Huntington said. "But we'll look at the Major League and Minor League market to see if there is somebody that complements our club."
Thomas spent less than a month on the Pirates' roster after being claimed off waivers Oct. 29. He had been expected to compete for a spot as a left-handed reliever in Spring Training, and that's still the Pirates' hope, assuming the lefty is able to sneak through waivers unclaimed.
"We think he can help," Huntington said. "We like Justin and are certainly hopeful that we are able to win the gamble. If he is able to get through, it really doesn't change his standing with the club. We just felt there were other young players that we had to get protected."
With Friday's moves, the Pirates have a full 40-man roster. If they want to make a selection in the Rule 5 Draft, they will have to clear yet another roster spot to do so.
When asked if the Pirates are likely to make a Rule 5 selection, Huntington remained noncommittal. "It's a possibility," Huntington said. "Not a definite. We feel like we've enjoyed some success in the last few Rule 5s and still have some time to evaluate rosters. If there's a luxury of picking second, it's that if there are two players we like, we can create the roster spot."
The Pirates left a number of Minor League players unprotected for the Rule 5 Draft, including infielder Shelby Ford, who was the club's third-round pick in 2006. However, if another team selects an unprotected player from the Pirates, that player would have to remain on the selecting club's 25-man roster through the entirety of the 2010 season or otherwise offered back to Pittsburgh for $25,000 -- half the cost for selecting him.
Jenifer Langosch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.