Escobar said he first felt the tightness while running the bases during the team's accelerated game on Tuesday. He traveled with the team on Wednesday to Osceola County Stadium, but after doing some running drills, Escobar decided not to play.
"It's just a little tight," Escobar said. "I decided to shut it down. I want to be cautious. Yesterday was a little sore. It was back-to-back days, so I didn't want to take any chances."
This is the fourth injury Escobar has suffered since joining the Nationals in 2005. That year, he didn't play in a game because of a fractured right foot. Last season, Escobar played in only 35 games because of a strained left hamstring and separated right shoulder. He still hasn't fully recovered from the shoulder injury.
Escobar insisted that he is not frustrated by having another injury. He pointed out there is still plenty of time during the exhibition season and that he should be ready to play in a few days.
"I'm just being cautious," he said. "I'm not concerned about it."
Escobar has proven in his limited action with the club that he is talented player, but the question remains, how long should the Nationals be patient with Escobar? He has been riddled with injuries for most of his career.
"He is coming into camp as a backup guy," manager Manny Acta said. "So, I mean, he's not pushing my patience. It's not like he is an everyday guy here."
No fool on the Hill: Right-hander Shawn Hill continues to show how badly he wants to be in the starting rotation. He pitched three solid innings and gave up a run on three hits against the Astros on Wednesday. It was Hill's second straight solid outing. He didn't allow an earned run against the Dodgers on Friday.
In Wednesday's game, after giving up an RBI single to Lance Berkman in the first inning, Hill retired seven of the next eight batters he faced.
"[In the first inning], he threw nothing but fastballs," Acta said. "He mixed up his pitches [after that] and he was impressive. We all know Shawn needs to be healthy. The rest will take care of itself."
Although he has had two solid outings, Hill said his confidence is not sky-high yet. He has at least four more starts to show that he belongs in the rotation.
"A lot of things can happen -- one way or the other," Hill said. "I can throw better or much worse. I feel good about the way I'm throwing right now. I'm trying to stay healthy and hopefully keep rolling."
Hill missed the second half of 2006 because of elbow problems.
Injury report: Shortstop Cristian Guzman played three innings at shortstop in the team's accelerated game on Wednesday morning. It's the first time he has played defense in a game since recovering from shoulder surgery.
Guzman will not play defense on Thursday, but will serve as the designated hitter against the Astros.
Welcome home: Acta returned to Osceola County Stadium for the first time since being named manager of the Nationals. Acta managed Class A Kissimmee at the stadium for three years.
He was greeted warmly by the grounds crew, fans, clubhouse workers and Julio Linares, the Astros' special assistant to the general manager for Dominican scouting and development. It was Linares who told Acta that he would be better off being a coach instead of a ballplayer.
"I spent 16 years of my baseball career [with the Astros]," Acta said. "I'm grateful to the Astros for everything. They signed me. They developed me as a player and a coach. I had to leave because I had to follow my dream of becoming a Major League coach. I was treated wonderfully, and there are still a lot of people in this organization that I owe a lot to."
Linares was like a proud father watching his son reach his ultimate dream.
"I don't have the words to describe how proud I feel," Linares said. "We have to give Manny a lot of credit for the way he carried himself from the time he signed to this day as a manager."
Booker, Bowie to see action: Relievers Chris Booker and Micah Bowie are expected to pitch in the team's accelerated game on Thursday. Booker has pitched one shutout inning, while Bowie has given up a run in two-thirds of an inning.
Stats of the day: Hill is 2-5 with a 6.90 ERA in nine big-league games, but four of those games were quality starts.
Did you know? Ryan Zimmerman leads the Nationals in Spring Training hits with six.
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Coming up: The Nationals return to Space Coast Stadium on Thursday at 1:05 p.m. ET afternoon to face the Astros for the second consecutive day. Right-hander Jason Jennings will get the nod for Houston, while righty Jason Simontacchi will go to the mound for Washington.
Simontacchi will make his second start of the spring. On Sunday, he pitched three innings and gave up two runs against the Dodgers.
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.