WASHINGTON -- Nationals manager Jim Riggleman said he has several candidates, including Nyjer Morgan, Ian Desmond, Roger Bernadina and Danny Espinosa, who could hit second in the order next year. But Riggleman said he would like to get a leadoff hitter for next year.

For most of this season, Morgan has been atop the lineup, but he is having a tough year. In the last two weeks, Espinosa has been at the top spot, but he may be better suited to hit lower in the order.

The Nats could also try to get a leadoff hitter via trade or free agency.

"The players will make the decision, whether it's Morgan, Espinosa, Bernadina, whoever," Riggleman said. "Somebody has to hit up there, and the one that doesn't will hit in the two spot. It's almost interchangeable.

"I think Nyjer can be a real plus for us in that two spot, but that means Desmond doesn't hit in the two spot, Bernadina [and Espinosa don't hit there, either]. It's going to have to work itself out at the end of the year and Spring Training."

Sore left shoulder ends Olsen's season

WASHINGTON -- Nationals left-hander Scott Olsen is done for the season due to a sore left shoulder. The last time he pitched was Sept. 17 against the Phillies.

In a bullpen session last week, Olsen had a difficult time getting loose.

"He was going to throw a bullpen session the other day," manager Jim Riggleman said. "He didn't feel really good. He has some aches and pains that indicted that trying to get him up in the bullpen just wouldn't work. It's not working for Scott."

Olsen, who was not available for comment, got off to a great start this season, but he was hampered by shoulder injuries that shelved him for a good portion of the season. After coming back from the injury, Olsen was hit hard and was demoted to the bullpen early in September. In two relief appearances, he allowed one run in six innings. Despite his success out of the bullpen, Olsen expressed displeasure being a reliever.

Olsen most likely played his last game as a member of the Nationals. He is arbitration-eligible and will likely be non-tendered after the season and become a free agent.

Zimmerman remains out with rib injury

WASHINGTON -- Nationals third baseman Ryan Zimmerman missed his fourth consecutive game with a right rib strain, and the injury is not getting any better, according to manager Jim Riggleman.

"As long as there isn't any change, he won't play. It has to get a lot better for him to play," Riggleman said about Zimmerman.

This is Zimmerman's second injury of the season. He missed several games in April because of hamstring problems.

The club has not ruled out Zimmerman missing the rest of the season. If that's the case, he will finish with a career-high .307 batting average, 25 home runs and 85 RBIs.