VIERA, Fla. -- Manager Jim Riggleman announced Sunday morning that Ian Desmond will be the Nationals' Opening Day shortstop, while the incumbent, Cristian Guzman, will be a utility player. Guzman will play all four infield positions.

In fact, Guzman was seen working out at second base before Sunday's Nationals-Braves game at Space Coast Stadium. Other than playing shortstop, the only position Guzman has played is third base, and that was during the 2008 All-Star Game at Yankee Stadium.

"I just have to take my time [playing the positions]. I'll play at third base, some games at short and second, a couple of games at first. You never know," Guzman said. "I've played my whole career at shortstop. I know [how to play the other positions] a little bit. I'll come to the park early and take some extra work at third base and second base. I think I'll get it."

Riggleman insisted that Guzman's right shoulder problems had nothing to do with the decision to play Desmond, but it didn't help that Guzman missed most of September because of the shoulder ailment and a lot of time this spring because he was trying to get his strength back in the shoulder. Guzman said the shoulder is 100 percent.

Desmond helped himself by hitting .280 with four home runs and 12 RBIs during the month of September. Entering Sunday's action, Desmond had a .278 batting average and a team-leading 12 RBIs. He's also played spectacular defense. In the second inning Saturday against the Braves, Omar Infante hit a sharp ground ball between short and third. Desmond made a nice diving stop and threw out Infante from his knees.

"Desmond has had an exceptional spring," Riggleman said. "And as we look into the future, this is a guy that could play for us in 2010 and '15. But for the year '10, he is playing really good in Spring Training, but he may not be playing well in May, so Guzman may be our shortstop. But to open the season, we'll give Desi a shot to hold that position down. We hope that works. If it does, then Guzzie has to be able to play some other positions."

Desmond received the news during batting practice.

"Opening Day is coming up," Riggleman told Desmond. "You are going to be our guy. I don't want you to change anything. I want you to keep on playing hard."

"It really wasn't much of a reaction. It was nothing, really," Desmond said after his talk with Riggleman. "I was playing hard and see if I could make it. I'm excited. It doesn't seem like it, but I am. I did everything I could to get better. I was hoping to make the team, but it feels good now to know that I'm on the team. It makes Spring Training a little better from here on out."

Desmond, 24, is coming off his best professional season, hitting a combined .321 with 11 home runs and 44 RBIs. His biggest highlight of 2009 came on Sept. 10. Desmond made his Major League debut, went 2-for-4, drove in four runs and helped the Nationals edge the Phillies, 8-7.

Prior to last season, Desmond never hit above .264 during his first five years in professional baseball. Desmond acknowledged he was overmatched during that period, but things started to click when he played in the Arizona Fall League in 2008. Coaches such as Troy Gingrich, Rick Eckstein and Devon White taught Desmond the proper way to hit.

"I had good Spring Trainings, but I never really believed I was a big-league player yet," Desmond said. "Now I believe, 'Hey, I can be a big league player. I can be a good big league player.' Hopefully, I'll be able to do that. Hopefully I'll be able to stick and be around a long time.

It would be difficult for Washington to trade Guzman, because he is making $8 million this season and is a 10-5 player, which means he has been in the league for 10 years and with the same club for five years, giving him the right to veto any trade. Guzman said he will not seek a trade and will do anything the team asks of him.

When told of the demotion, Guzman didn't respond to Riggleman. Guzman took it like a professional.

"I didn't say anything. I just listened," Guzman said. "[Riggleman] told me how they were going to give Desmond the opportunity. I like [Desmond]. I'm happy for him. He is going to be a real good player. If they need me in a different position, I'll play it. This is the last year of my contract, so I have to play wherever they want me to play -- just do my job."