16 PAUL LO DUCA
2007 key stat: Hit .341 against left-handers for Mets.
Best case: Becomes valuable bat in lineup and steady hand for young pitchers.
Worst case: Injuries force long stints on the disabled list.
23 JOHNNY ESTRADA
2007 key stat: With Brewers, threw out six of 79 runners trying to steal.
Best case: Is able to spell Lo Duca and give Nationals a solid bat off the bench.
Worst case: Injuries hamper his production, and he becomes a defensive liability.
2007 Key Stat: Had five game-tying or go-ahead hits.
Best case: Sticks around because of injuries to Lo Duca and Estrada and becomes Nats' catcher of the future now.
Worst case: Gets sent down to Harrisburg within a week and remains there all year.
24 NICK JOHNSON
2007 key stat: Missed season with broken leg.
Best case: Picks up where he left off in 2006, hits .290 with 28 homers and 100 RBI.
Worst case: Misses large chunks of time with injuries and loses starting job to Dmitri Young.
21 DMITRI YOUNG
2007 key stat: .366 average at RFK Stadium was highest in park's history.
Best case: Winds up as team's first baseman, hits .300 with 80 RBI.
Worst case: Can't keep himself in shape well enough to make a difference, languishes on bench.
2 FELIPE LOPEZ
2007 key stat: Hit just .218 with runners on base.
Best case: Finds All-Star form of 2005 playing in a new park, hits 25 homers and drives in 90 runs.
Worst case: Loses starting job to Belliard, chafes at backup role and becomes center of trade talk.
10 RONNIE BELLIARD
2007 key stat: Led team with 17 games of three hits or more.
Best case: Continues where he left off last September; hits .300 as starting 2B.
Worst case: Is ineffective as a utility infielder and pinch hitter.
15 CRISTIAN GUZMAN
2007 key stat: In 46 games, .380 on-base percentage was 43 points higher than previous best.
Best case: Builds on torrid spring, lays off bad pitches, hits .300 and gets contract extension.
Worst case: Questions about effort resurface and strikeouts reach triple digits.
11 RYAN ZIMMERMAN
2007 key stat: 18 game-winning RBI ranked second in MLB.
Best case: Takes next step in career progression and hits .300 with 30 homers and 110 RBI.
Worst case: Can't lay off breaking balls low and away, hits .265 and strikes out 125 times.
8 AARON BOONE
2007 key stat: Batted .286 in 69 games with Florida.
Best case: Becomes valuable bat off the bench — we hear he's gotten a big late-game hit at some point in his career.
Worst case: Spends large chunks of the season on the disabled list like he did last year.
34 ELIJAH DUKES
2007 key stat: Homered once every 18.4 at-bats with Tampa Bay.
Best case: Given a full season, cashes in on potential and hits 30 homers.
Worst case: Can't hit major league pitching every day or finds trouble off the field and spends most of his time on the bench.
1 WILLIE HARRIS
2007 key stat: Hit safely in 54 of 78 starts.
Best case: Finds a niche as utility player and source of speed off the bench.
Worst case: Loses out to Nationals' young talent, heads back to minor leagues.
25 AUSTIN KEARNS
2007 key stat: Tied for eighth in NL with nine outfield assists.
Best case: Finally shows power stroke full-time, hits 25 homers with 85 RBI.
Worst case: Frequent strikeouts prompt Nationals to bench him for Dukes.
29 RYAN LANGERHANS
2007 key stat: Made just one error in 103 games with Nationals.
Best case: Uses strong arm and solid glove to stay on team as extra outfielder.
Worst case: No room for him in crowded outfield.
12 ROB MACKOWIAK
2007 key stat: Drove in 36 runs in 85 games with Cubs before being traded to San Diego.
Best case: Provides some pop off the bench and as occasional starter.
Worst case: Strikes out too much, doesn't hang around on big-league roster.
44 LASTINGS MILLEDGE
2007 key stat: Hit .304 with runners in scoring position.
Best case: Builds on strong spring and hits 25 homers while flashing strong range in center.
Worst case: Struggles with off-speed pitches, hits .250 with 110 strikeouts.
26 WILY MO PENA
2007 key stat: Struck out 94 times in 110 games.
Best case: Learns to be more selective at the plate, stays healthy and hits 30 homers as Nats' left fielder.
Worst case: Starts slow after injury, hits .240 with 125 K's.
56 LUIS AYALA
2007 key stat: Posted 1.23 ERA in 14 appearances on zero days rest.
Best case: Continues to be a tough matchup out of the bullpen; matches last season's results over 70 appearances.
Worst case: Elbow troubles resurface, he fails to stay healthy long enough to make an impact.
57 JASON BERGMANN
2007 key stat: Allowed three runs or less in 15 of 21 starts.
Best case: Continues development as a starter, posts double-digit wins with ERA under 4.
Worst case: Lands on DL and doesn't show Nationals he's capable of becoming a reliable starter.
47 MATT CHICO
2007 key stat: Led team with 167 innings pitched.
Best case: Makes team as back-of-the-rotation starter who can eat innings.
Worst case: Struggles with control, can't stay ahead of hitters and heads to minors.
43 JESUS COLOME
2007 key stat: Established career high in appearances with 61.
Best case: Posts 65 appearances, drops ERA under 3.50 and continues to be valuable late reliever.
Worst case: Regresses from career year in 2007, loses seventh-inning spot.
32 CHAD CORDERO
2007 key stat: In 76 appearances, only 46 were save opportunities.
Best case: Continues to be reliable closer — only he gets 45 saves on a better team.
Worst case: Trend of rising ERA the last two years continues as hitters start to figure him out.
38 JOEL HANRAHAN
2007 key stat: Pitched just 51 innings in 12 starts.
Best case: Adapts to role as reliever, uses eye-popping stuff to make 50 late-inning appearances.
Worst case: Can't adjust to coming in with runners on base, posts 6.00 ERA.
36 RAY KING
2007 key stat: Made 67 appearances for Nationals and Brewers.
Best case: Expands beyond specialist role, posts sub-3.00 ERA in more than 80 innings of work.
Worst case: Lefties figure him out and he loses spot to younger arm.
31 JOHN LANNAN
2007 key stat: Posted 4.15 ERA in six starts.
Best case: Wins 10 games and establishes self as bona-fide major league starter.
Worst case: Spends year at Class AAA Columbus waiting for his turn in the majors.
45 ODALIS PEREZ
2007 key stat: Allowed homer once every 9.8 IP, second-best mark of career.
Best case: Fulfills prediction of 200 innings, 15 wins.
Worst case: Gets hammered early, team looks to move him to make room for young arm.
17 TIM REDDING
2007 key stat: Held runners to .206 average with runners in scoring position.
Best case: Wins 12 games as reliable back-of-the-rotation presence.
Worst case: Can't get lefties out, loses rotation spot to midseason call-up.
51 JON RAUCH
2007 key stat: Allowed just four more hits (75) than he had strikeouts.
Best case: Continues to establish self as top-end setup man with 80 strikeouts and 2.50 ERA in 85 appearances.
Worst case: Gives up too many homers and sees ERA balloon to 4.50.
52 SAUL RIVERA
2007 key stat: Gave up just one homer in 93 innings.
Best case: Continues to be a pleasant surprise out of bullpen with 3.20 ERA in 75 appearances.
Worst case: Third year in NL gives hitters enough time to adapt; ERA tops 4.25.