BOSTON -- In preparation for the Rule 5 Draft on Dec. 9, the Red Sox added three players to their 40-man roster on Friday. The group is headlined by catching prospect Luis Exposito and also includes righty Stolmy Pimentel -- who pitched in the Futures Game last July -- and infielder Oscar Tejeda.

Boston's roster is now at 39.

Players who signed when they were 19 or older (e.g. college draftees) four years ago, or players who signed at 18 and younger (international signees or high school draftees) five years ago, are all eligible for the Rule 5 Draft if they're not placed on 40-man rosters.

For example, any unprotected college draftees from the 2007 Draft or high school Draft picks from the Class of '06 are up for grabs.

One candidate to be taken by another team in the Rule 5 Draft is Daniel Turpen, the righty reliever the Red Sox acquired from the Giants for Ramon Ramirez back in July. Turpen made 12 appearances for Double-A Portland, going 2-1 with a 4.91 ERA.

Though Exposito isn't Major League-ready just yet, the Red Sox are intrigued by his offensive potential. In 2010, he hit .260 with 39 doubles, one triple, 11 home runs, 94 RBIs, 65 runs scored and 55 walks in a career-high 125 games for Double-A Portland in 2010. The 23-year-old also caught 30 out of 80 baserunners who attempted to steal on him for a 37.5 success rate, leading the Eastern League.

Pimentel, 20, went 9-11 with a 4.06 ERA in 26 starts for Class A Salem in 2010, notching a team-high 102 strikeouts. He retired the only two batters he faced in the Futures Game.

Tejeda had a terrific 2010 season for Salem, making the midseason and postseason All-Star Team for the Carolina League. He hit .307 with 32 doubles, five triples, 11 homers and 69 RBIs while stealing 17 bases in 126 games. He was signed by the Red Sox as an international free agent on July 2, 2006.

Boston's complete roster is as follows:

Pitchers (18): Scott Atchison, Daniel Bard, Josh Beckett, Michael Bowden, Clay Buchholz, Taylor Buchholz, Robert Coello, Felix Doubront, Matt Fox, John Lackey, Jon Lester, Daisuke Matsuzaka, Andrew Miller, Hideki Okajima, Jonathan Papelbon, Stolmy Pimentel, Junichi Tazawa and Tim Wakefield. 

Catchers (3): Luis Exposito, Jarrod Saltalamacchia and Mark Wagner. 

Infielders (10): Lars Anderson, Brent Dlugach, Jose Iglesias, Jed Lowrie, Yamaico Navarro, David Ortiz, Dustin Pedroia, Marco Scutaro, Oscar Tejeda and Kevin Youkilis.

Outfielders (8): Mike Cameron, J.D. Drew, Jacoby Ellsbury, Ryan Kalish, Darnell McDonald, Daniel Nava, Eric Patterson, Josh Reddick.