WASHINGTON -- The Astros claimed right-hander Cesar Carrillo off waivers from San Diego on Wednesday. To make room for Carrillo on the 40-man roster, infielder Edwin Maysonet was designated for assignment.

The 26-year-old Carrillo was the Padres' first-round pick, 18th overall, in the 2005 First-Year Player Draft and made three starts for San Diego in 2009, going 1-2 with a 13.06 ERA in three starts. This season, he was 5-14 with a 5.60 ERA in 27 starts at Triple-A Portland.

However, he has been designated for assignment twice this month. The Padres designated him Sept. 1, and Carrillo was claimed off waivers by Philadelphia on Sept. 9. The Phillies waived him and San Diego reclaimed the right-hander on Sept. 15 before designating him for assignment on Sept. 20.

Carrillo will not see time with the Astros this season.

Maysonet hit .276 with a homer and seven RBIs in 46 games for Houston from 2008-09, but played exclusively in the Minors in 2010, batting .248 with two homers and 40 RBIs in 90 games for Triple-A Round Rock and the Rookie League Gulf Coast Astros.

Sore Bourn, Pence out of Astros' lineup

WASHINGTON -- Center fielder Michael Bourn missed a third straight start Wednesday night against the Nationals because of a strained right side muscle, and the Astros were also minus right fielder Hunter Pence, who is slowed by discomfort in his right hip flexor.

Pence was hoping to be available to pinch-hit -- only in a situation where he wasn't required to run a hit out hard -- but that decision was to be a game-time decision based on how he did in batting practice.

"It's feeling better," Pence said. "I'd like to think I could I could go out there and pinch-hit today, but I'll have to go out there [during batting practice] and see how it feels."

While Pence described his pain as "mild" discomfort, Bourn reported little progress in his recovery.

"Not too much difference," he said when asked for a progress report. "A little less sore, but I'm not going to run or do anything today."

Bourn sustained his injury taking successive swings in Sunday's game. Pence left after batting in the first inning Tuesday night because the hip flexor problem doesn't allow him to quickly accelerate.

Astros' injuries open door for Bourgeois

WASHINGTON -- Injuries to the Astros' Michael Bourn and Hunter Pence have created playing time for outfielder Jason Bourgeois, who doesn't intend to waste his opportunity to make a positive late-season impression.

"I don't wish that on anybody with injuries. I wish good health for all players. But if the opportunity presents itself like this, it's something I've been preparing for and something I'm ready for," said Bourgeois.

Knowing that he's going to be in the lineup for more than a quick look-see -- Wednesday was his third straight start in place of Bourn -- means an unexpected chance for the 28-year-old.

"I'm a guy that doesn't have a lot of time, so I want to make my presence felt," he said. "A couple more weeks left is a good time to put good positive [feelings] in the coaches and everybody's heads. Make a lasting impression."

Astros manager Brad Mills likes the speed and aggressiveness Bourgeois brings to the table but wants to make sure he uses those attributes to his advantage. After Bourgeois was thrown out trying to steal third for the third out in the second inning Tuesday night, Mills met with Bourgeois and third-base coach Dave Clark before Wednesday's game.

The trio also went over a situation from Wednesday night's loss in which Bourgeois couldn't get a bunt down.

Mills' message to Bourgeois: Play your game and don't feel like you have to replace Bourn's offense in the lineup.

"It's important for Jason Bourgeois to be Jason Bourgeois -- not Michael Bourn, [but] Jason Bourgeois," said Mills.

Mills sees positives in Lindstrom's struggles

WASHINGTON -- Despite the fact that Matt Lindstrom has allowed runs in three of his past four outings entering Wednesday, Astros manager Brad Mills isn't concerned that the right-hander is doing any more than working through the kind of rough patch every reliever goes through at some point during each season.

Lindstrom walked a hitter and allowed three singles in the eighth without retiring a batter in Wednesday's 8-4 loss to the Nationals. His ERA has risen from 3.65 to 4.59 after Lindstrom allowed six runs in 1 2/3 innings over his past four outings.

Since coming off the disabled list for a back problem on Sept. 1, Lindstrom has been mostly effective. Mills doesn't think his recent struggles can be tied to the previous injury.

"Are things connected? When they start stringing [bad outings] together, there's a possibility they might be connected," Mills said. "But at the same time, he feels strong, his back feels good, his arm feels good, his velocity is very good. His pitches have a lot of crispness."

Mills said he thinks Lindstrom's issues are more related to pitch selection and location.