In anticipation of next week's Winter Meetings, and possibly of Friday's deadline to make contract offers to arbitration-eligible players, the Pirates on Wednesday reshuffled their 40-man roster.

The club designated for assignment infielders Matt Hague and Yamaico Navarro, needing their spots for two players acquired from Kansas City in trade: First baseman Clint Robinson and right-hander Vin Mazzaro, in exchange for young pitching prospects Luis Rico and Luis Santos.

In another transaction, Pittsburgh acquired right-hander Zach Stewart from Boston for a player to be named later.

All three newcomers have limited Major League experience, the least by the most intriguing of them: Robinson, a strapping 6-foot-5, 240-pound lefty swinger who had a four at-bat big league debut last summer.

Three of those at-bats came in PNC Park, during an Interleague series. Robinson, 27, immediately looms as an alternative to two arbitration-eligible first basemen on the roster, Gaby Sanchez and Garrett Jones. Robinson also slides in as a replacement for Hague, who was given a fair shot to make an impression last season (with a three-week run as the primary first baseman), but could hit only .229, with little extra-base pop.

At Triple-A Omaha last season, Robinson batted .292 with 13 homers and 67 RBIs. Perhaps most impressive for a guy with his big swing: He had more walks (79) than strikeouts (65) in 570 plate appearances.

Mazzaro, 26, has a 15-21 record with an ERA of 5.22 in four seasons split between the A's, who'd drafted him in the third round in 2005, and the Royals. His 66 big league games include 45 starts.

Neither Rico, 19, nor Santos, 21, has yet to pitch domestically. Both had been in the Pirates organization for two years, pitching last summer in the Dominican summer league.

Stewart, 26, has been on the move since being the Reds' third-round choice in the 2008 Draft. This is already the fourth trade in which he has been involved, having gone from the Reds to the Blue Jays to the White Sox to the Red Sox. The veterans he has exacted in those moves -- Scott Rolen, Edwin Jackson, Kevin Youkilis -- hint of Stewart's potential.