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03/08/12 6:30 PM ET

Harper likely to miss 2-3 days with tight calf

VIERA, Fla. -- Nationals right fielder Bryce Harper was expected to start against the Astros on Thursday, but was a late scratch because of left calf tightness. He is expected to be out two to three days.

Eury Perez replaced Harper in the lineup for Washington's 8-0 win. Perez played center field, while Brett Carroll was switched from center to right.

Harper said he woke up Thursday morning with the tightness. He then went to Space Coast Stadium and exercised on the bike to loosen the calf, before doing some outfield drills. But the pain didn't go away.

"I never felt it before," Harper said. "That was the weird thing. I felt it this morning. I have no clue what's going on right here. I came in and tried to ride the bike and tried to loosen it up. I didn't feel it when I swung [the bat]. I felt it getting reads in the outfield."

Entering Thursday's action, Harper was 5-for-11 (.455) with five singles. His five hits led the Nationals. Manager Davey Johnson said he was going to give Harper every chance to be Washington's everyday right fielder.

Something 'clicks' for Jackson's mechanics

VIERA, Fla. -- Nationals right-hander Edwin Jackson made his second start of the spring and was solid in an 8-0 victory over the Astros at Space Coast Stadium on Thursday afternoon.

Jackson pitched four shutout innings, allowed two hits and struck out three batters, all of which came on breaking balls.

"Edwin Jackson was superb. You can quit writing about all his mechanics and all that," manager Davey Johnson said. "He is as good as it gets. Everything about him."

Jackson's mechanical problems appear to be a thing of the past. He doesn't know how he fixed them. It was about being relaxed and having fun. Jackson even went back to pitching from a full windup, which was giving him problems last year. Opponents hit over .330 when he pitched from the windup.

"I felt better than last time, definitely," Jackson said. "I was able to go out and find a rhythm early. That's what I'm been trying to do -- find something that feels comfortable. I was able to do that today. Obviously, it's still a work in progress. You still try to fine-tune a couple of things.

"But, overall, for the most part I felt good. When you are going good, you really don't know what it is. When you are going good, you are going good. Something just clicked. Whatever mechanics I have, I was able to just continue to repeat them and throw pitches across the plate."

Detwiler enhances chances with perfect relief

VIERA, Fla. -- Nationals left-hander Ross Detwiler pitched three shutout innings in an 8-0 victory over the Astros at Space Coast Stadium on Thursday. He struck out three batters without allowing a hit or a walk.

Manager Davey Johnson felt Detwiler could have gone another inning because of a low pitch count, but needed relievers Ryan Perry and Henry Rodriguez to get some work in the game.

It will be interesting what role Detwiler will play on the team. He is out of options and most likely will start the season as a long reliever. Detwiler was in that role briefly last season before being put in the rotation.

"It's all pitching once you get down to it," Detwiler said. "If I'm in the bullpen, I have to rely on those guys to teach me a routine ... find something that works for me."

LaRoche progresses, homers in Minors game

VIERA, Fla. -- Nationals first baseman Adam LaRoche played in another Minor League game on Thursday and looked much better than he did the day before.

LaRoche had five plate appearances and one hit, but that hit was a homer against a lefty pitcher. The left-handed-hitting slugger also had a walk and a sac fly. Although his left foot was still sore, LaRoche was also able to run the bases.

"I hit four balls off the end of the bat yesterday, so ... I felt I had to come back today and redeem myself," LaRoche said. "It felt good. I ran around the bases a little bit, even on some outs. ... It feels a lot better today than it did two days ago. I'm not as concerned about my swing as I am with my foot, [and I'm making sure] things are together there."

LaRoche is hoping to play in his first Grapefruit League game on Saturday against the Mets.

Prospect Perez impressing Nationals

VIERA, Fla. -- Nationals outfield prospect Eury Perez won't make the Opening Day roster, but he has opened some eyes during Spring Training.

Entering Friday's action against the Cardinals, Perez is 4-for-9 (.444), including two hits against the Astros on Thursday. Manager Davey Johnson said he has seen an improvement in Perez's game.

"What I saw three years ago, he is so much better," Johnson said. "His swing is short and compact. He has come a long way. He really looks good to me. His standing in the organization was high to begin with. He has only enhanced it."

Perez is projected to land in the big leagues in about two years. He played for Class A Potomac last year, hitting .283 with one homer, 41 RBIs and 45 stolen bases.

Blanco, Morse on the mend

VIERA, Fla. -- Nationals infielder Andres Blanco wasn't available for Thursday's game against the Astros because of an ear infection. He was expected to have a procedure performed Thursday, and there isn't a timetable on when he will return to action.

Blanco is hitless in five at-bats this spring, and is looking to make the team as a bench player.

Michael Morse, who has missed the last three games because of a strained lat, has been given the go-ahead to swing the bat, but he still has a problem throwing the baseball.

Within the next three or four days, Morse will get some at-bats by playing in Minor League games, according to manager Davey Johnson.

Morse has played in only one exhibition game and is 1-for-2 with a run scored.

Worth noting

• According to manager Davey Johnson, the Nationals are expected to make their first round of cuts on Monday. The original plan was for cuts after Saturday's split-squad games, but Johnson wants to make sure he has observed every player before making the final decisions.

• Johnson will manage the Nationals against the Mets at Space Coast Stadium on Saturday, while bench coach Randy Knorr will manage the other split-squad in Lakeland, Fla.

• For the split-squad games, Johnson has decided that Chien-Ming Wang will pitch against the Mets, while John Lannan will throw against the Tigers.

Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the time. He also could be found on Twitter @WashingNats. This story was not subject to the approval of Major League Baseball or its clubs.