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05/27/10 10:18 PM ET

Olsen's throwing session postponed

Nats cautious with injured lefty due to rainy conditions

SAN FRANCISCO -- Nationals left-hander Scott Olsen did not play catch as expected on Thursday because of the rainy conditions at AT&T Park and Olsen's left shoulder wasn't deemed strong enough.

There isn't any timetable as to when Olsen will do any kind of throwing, but he will rest his shoulder a few more days, according to manager Jim Riggleman.

When he went on the disabled list on Saturday because of shoulder tightness, Olsen was told not to throw for five days. Five days have already passed and he's yet to make an attempt. The team has not ruled out Olsen missing more than two starts, with right-hander J.D. Martin a likely candidate to take his turn in the rotation.

On Friday against the Orioles, Olsen pitched three innings, allowing four runs on six hits, one of them a two-run homer to Adam Jones in the second inning. An inning later, he allowed a two-run single to Craig Tatum.

Olsen was scheduled to hit in the bottom of the third inning, but Livan Hernandez came in as a pinch-hitter and struck out.

Olsen is 2-2 with a 3.77 ERA in eight starts for the Nationals.

Patience pays for Willingham

SAN FRANCISCO -- Entering Thursday's action, Nationals outfielder Josh Willingham led the National League with a .434 on-base percentage. It helps that he leads the league in walks with 34. Willingham said he doesn't have a new approach at the plate. It's just a matter of swinging at the right pitch.

"If I don't get my pitch early on the count, I just don't swing," said Willingham, who is hitting .277 with eight home runs and 29 RBIs. "If I get a good pitch to hit, I'm going to swing first pitch."

Stammen has quality start

SAN FRANCISCO -- Right-hander Craig Stammen was solid during the Nationals' 5-4 loss to the Giants at AT&T Park on Thursday afternoon.

Stammen lasted 6 1/3 innings, allowing two earned runs on five hits. It was his first quality start since May 7 against the Marlins. Stammen needed to have a good outing because he could be the odd man out of the rotation once right-hander Stephen Strasburg is called up next month.

Before Thursday's game, Stammen was 1-2 with a 5.96 ERA. Manager Jim Riggleman did not indicate if Stammen is in danger of losing his spot in the rotation.

"We have a lot of confidence in him," Riggleman said before Thursday's game. "When we send him out there, we think he has a chance to shut hitters down. We are waiting for it to all come together."

Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.