Candidates for the Nationals bullpen this season (barring injuries) look like:
Name: Throws: 2011 Stats:
Sean Burnett: L 56.2 IP 15 HLD 33K 3.81 ERA
Tyler Clippard: R 88.1 IP 38 HLD 104K 1.83ERA
Ross Detwiler: L 66.0IP 5QS 1HLD 41K 3.00ERA
Cole Kimball: R 14.0IP 0HLD 11K 1.93ERA
Brad Lidge: R 19.1IP 8HLD 1SV 23K 1.40ERA
Drew Storen: R 75.1 IP 43SV 74K 2.75ERA
Craig Stammen: R 10.1IP 1HLD 12K 0.87ERA
Yunesky Maya: R 32.3IP 1QS 15K 5.23ERA
Ryan Mattheus: R 32.0IP 8HLD 12K 2.81ERA
Tom Gorzellany: L 105IP 6QS 4HLD 95K 4.03ERA
John Lannan: L 184.2IP 16QS 106K 3.70ERA
Chen-Ming Wang: R 62.1IP 4QS 25K 4.04ERA
Henry Rodriquez: R 65.2IP 10HLD 2 SV 70K 3.56ERA
Early in the season when pitchers are still being stretched out, it's more common to see teams keep a short bench and an extra guy in the pen to start the season, but until the 5th starter is needed you may see both Wang and Lannan pitch out of the pen the first week or so taking care of that need. Spring Training will probably decide whether Johnson feels like he needs a deeper bench or a deeper pen to start the season.
The fact that Lannan, Gorzellany, Detwiler and Burnett are the only LH in the competition could work against Lannan in the 5th starter competition. If Detwiler is sent to AAA to start the season, that creates more of a need for a LHP versus a RHP in the pen, so if things are fairly even between Wang and Lannan, Lannan could end up in the pen out of concerns for balance.
Storen established himself as quite a young closer last season, but when Lidge is healthy he's one of the best in the game. This could turn into a 2-headed closing monster before long. The Nationals came dangerously close to dealing Storen this offseason for a CF, so maybe they aren't as confident in them as they should be, but either way those two should start at the back of the pen in some form. After that Clippard and Burnett should be 1-inning options for the 7th/8th area as a R and L option.
There are 12 men in the mix for an 8 or 9 man BP (my guess is 8) which means that 4 guys aren't going to make the opening day roster. Detwiler could be sent to AAA to be a starter, which means that 3 more out of Rodriguez, Kimball, Mattheus, Maya, and Stammen are probably headed to AAA. Overall, it's one of the more solid BP in baseball as is, with 2 solid closing options (Lidge, Storen), two established set up men both R and L (Clippard, Burnett), and a couple guys who could be 3rd starters on some teams in the long roles (Lannan, Wang).