The Nationals added two pitchers — reliever Erik Davis and starter Nathan Karns, both right-handers — to the 40-man roster on Tuesday night to protect them from the Rule 5 draft. In only choosing to add only those two to the roster, the Nationals’ roster stands at 38 players with two open spots for flexibility if they add players via trades or free agency — but by doing so, the Nationals are risking leaving a handful of decent prospects available for other clubs to claim in a few weeks.

The Nationals protected Davis and Karns, two of their best arms eligible for the Rule 5 draft. Davis, 26, was acquired before the 2011 season from the San Diego Padres for utility infielder Alberto Gonzalez, and posted the best season of his career in his first full one as a reliever. Karns, 24, is an inspiring story, a pitcher with potential who was drafted in 2009, sidelined until 2011 because of a shoulder injury and was named the 2012 Nationals minor league pitcher of the year.

Between Class AA Harrisburg and Class AAA Syracuse, Davis went 8-3 with a 2.71 ERA over 73 innings in 48 games, striking out 74 and walking 20. He was drafted out of Stanford by the Padres in the 2008 draft. He is 3-0 with a 0.56 ERA and opponents are hitting .155 batting off him in 14 appearances in a stint with Gigantes del Cibao in the Dominican Winter League. 

After tossing only 55 1/3 innings in 2011, Karns reached Class A Potomac this season and posted a 2.17 ERA over 116 innings and striking out 148 between there and Class A Hagerstown. He doesn’t have much experience but the Nationals saw the talent, signing the big right-hander for well over slot when they drafted him in the 12th round in 2009. 

There are two kinds of players eligible for the Rule 5 draft: those who were 18 or younger when they signed and have at least five years of minor league service, and those who were 19 or older when they signed and have at least four years of minor league service. Essentially, that’s players drafted out of college in 2009 (or earlier) or high school in 2008 (or earlier) who are not currently on 40-man rosters. In the Rule 5 draft, teams can select any player from that pool. They must then pay $50,000 and keep that player on their 25-man roster for a full season. If not, they have to return him to the original team.

The Nationals made the moves late Tuesday because 11:59 p.m. was the deadline to protect players who would have been eligible for the Rule 5 draft, which will take place Dec. 6 on the final day of the winter meetings in Nashville. Davis and Karns, by virtue of being added to the 40-man roster, will be invitees to major league camp in spring training.

The Nationals left a handful of players unprotected for the Rule 5 draft, notable among them outfielder Destin Hood, infielder Jeff Kobernus, left-handed pitcher Danny Rosenbaum and right-handed pitcher Rob Wort. Kobernus, one of the fastest players in the Nationals’ minor league system, and Wort, who has little experience but a big arm, could be likely targets of other teams.

Here’s the breakdown of the 40-man roster as it stands Tuesday night:

Outfield (7): Roger Bernadina, Corey Brown, Bryce Harper, Tyler Moore, Michael Morse, Eury Perez, Jayson Werth

Infield (8): Ian Desmond, Danny Espinosa, Steve Lombardozzi, Chris Marrero, Anthony Rendon, Carlos Rivero, Chad Tracy, Ryan Zimmerman

Catcher (5): Jesus Flores, Sandy Leon, Wilson Ramos, Jhonatan Solano, Kurt Suzuki

Pitcher (18): Tyler Clippard, Erik Davis, Ross Detwiler, Christian Garcia, Gio Gonzalez, Tom Gorzelanny, Nathan Karns, Cole Kimball, John Lannan, Ryan Mattheus, Yunesky Maya, Ryan Perry, Matt Purke, Henry Rodriguez, Craig Stammen, Drew Storen, Stephen Strasburg, Jordan Zimmermann.