The following is the second in a series of weekly stories on MLB.com examining each Major League club, position by position. Each week until Spring Training camps open, we'll preview a different position. Today: Corner infielders.

It's a given that Ryan Zimmerman will be the Nats' starting third baseman, with Aaron Boone as his backup. Besides being one of the best defensive players in the game, Zimmerman has been Washington's most consistent run producer the last two years.

In 2007, Zimmerman got off to a slow start, but ended up hitting .282 after the All-Star break and driving in 91 runs. After the season ended, Zimmerman had left wrist surgery to remove a hamate bone. General manager Jim Bowden said recently that Zimmerman is expected to be 100 percent by Spring Training.

Boone will be one of the first hitters off the bench in the late innings or if Zimmerman gets hurt. Boone can play every infield position and provide some pop with the bat. Last season, Boone played in 69 games for Florida, and he hit .286 with five home runs and 28 RBIs. He was playing regularly at first base before a left knee injury in late June put him out for the rest of the season. Boone's knee is now considered 100 percent healthy.

"He gives us a right-handed bat off the bench," Bowden said. "He is a clutch hitter. We have a winning player with a winning attitude. He makes us a lot better -- depth wise."

Rob Mackowiak is another Nats player who can back up at third base. He is a career .262 hitter who can also play all three outfield positions, as well as first and second base. Mackowiak hit a combined .278 with six homers and 36 RBIs in 85 games with White Sox and Padres last season. He hit .283 (13-for-46) against left-handed pitching.

But the big question is who will be the starting first baseman for the Nationals. It appeared that Nick Johnson would be the choice once he recovered from his broken right leg, and Dmitri Young said more than once that he would be switched to the outfield. But Bowden said last week that Young is the team's starting first baseman entering Spring Training.

Young had a calming influence on young players last season, helping to improve the mood in the clubhouse from the previous year. He was always spotted giving rookies a helping hand. Young is now being asked to be Elijah Dukes' mentor this coming season, a role Young has gladly accepted.

Young was one of the Nationals' best hitters in 2007, hitting .320 with 13 home runs and 74 RBIs. It earned him the National League Comeback Player of the Year Award.

Washington Nationals • Catchers: Lo Duca takes over • Corner IF: Johnson a wild card • Middle IF: Battle brewing at short • Outfielders: New faces join Kearns • Starters: Health is key for Nats • Bullpen: Corps has proven its worth • Bench: Looking for improvement

Johnson didn't play a game last season because of a leg injury suffered in a collision with Austin Kearns on Sept. 23, 2006. Johnson had some setbacks along the way. He had a sore right knee and hip.

When he is healthy, Johnson usually has a high on-base percentage and can bat second or third in the lineup.

"As we walk into Spring Training, Dmitri Young is our first baseman," Bowden said. "He deserves it. He finished in the top 10 in hitting. He improved defensively, and his leadership skills in the clubhouse were phenomenal. So he is obviously the first baseman.

"I talked to Nick Johnson, and he is healthy. He is already running the bases. He is doing extremely well. He feels great. I think we can all be optimistic there is a good possibility that he comes into Spring Training at 100 percent, which will create good competition. It's healthy for a club."

A few weeks ago, Johnson talked about his recovery.

"Things are going real well," he said. "I have therapy three days a week. I'm trying to get healthy and ready to play [this season]."

Matt Whitney, a Rule 5 Draft pick, is listed as the fourth first baseman on the Nationals' depth chart. Whitney led the Indians' Minor League system with 32 home runs and 113 RBIs in a combined 128 games with Class A Lake County and Class A Kinston. Baseball America named Whitney the 10th-best prospect in the Carolina League following the season, after he hit .288 with 16 homers, 49 RBIs and a .549 slugging percentage in 57 games with Kinston.

"Whitney is a Jesus Flores type -- [he is] not ready for the Major Leagues, but certainly has tremendous potential," Bowden said. "Whitney hit over 30 home runs last year. He has a tremendous bat and great power. He got healthy for the first time, and he did it in two levels."