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8/13/2014 12:50 A.M. ET

Setback delays Springer's return two more weeks

Astros rookie slugger, GM Luhnow confident he'll play again this season

HOUSTON -- The Astros are going to have to deal with life without George Springer for at least a couple of more weeks.

Springer, the team's up-and-coming rookie outfielder, will be out at least two more weeks to give his left quad strain more time to heal. The team said Tuesday that Springer aggravated the injury and recently underwent an MRI. A team doctor examined him Monday and prescribed two more weeks of rest.

"We weren't sure if it was going to be a thing that he could work through quickly, but after the doctor saw him [Monday] night, he made the determination he needs to take some time off and let it heal," general manager Jeff Luhnow said. "It's unfortunate, because we felt like he was a couple of days away from rejoining our team and clearly is a missed presence in the lineup and in the outfield. We're going to have to wait until he's completely healthy. We don't want to take any more risks."

Springer played three games on a Minor League rehab last week in Class A Quad Cities and tweaked his quad running the bases.

Springer made his much anticipated Major League debut in mid-April and took off in May, being named American League Rookie of the Month. He's played in 78 games, hitting .231 with 20 homers, 51 RBIs and a .336 on-base percentage.   

"It's tough, just because I'm a competitor and I want to go out there and help the team, but I've got to get healthy and see what happens," Springer said. "I want to go out there and compete with these guys and be able to help and not be a cheerleader. I want to be able to play, but you've got to be smart."

Springer will travel with the Astros on Wednesday night before they open a 10-game road trip on Thursday at Fenway Park against the Red Sox. Springer, who's from Connecticut, grew up a huge Red Sox fan, but won't get the opportunity to play in Boston.

"It'll be tough, but I think it's harder to not play in general," he said. "It's not just because we're going to play in Boston and all that stuff. I want to play every day here."

Springer remains confident he'll get on the field again this year.  

"That's the ultimate goal is to get back out there," he said. "I'll get stronger and keep doing what I've got to do in order to play."

Luhnow believes Springer will play most of September.

"This type of injury, he should be able to come back from," he said. "Obviously, we're going to be very cautious with bringing him back, but we still have plenty of time. I expect he'll play the month of September here."   

Losing Springer for an extended time was softened by the news Tuesday that outfielder Dexter Fowler would return Wednesday for the first time since June 26. Meanwhile, outfielder Alex Presley is also close to returning.

"Obviously, losing George Springer is a big void for our ballclub," manager Bo Porter said. "He is a player that can impact a game in so many ways. We missed him the entire time in which he's been out already, and we will continue to miss him. At the same time, the guys that are going to have the opportunity to get that playing time, they can use the opportunity to take advantage of it."

Fowler back from intercostal strain today

HOUSTON -- Center fielder Dexter Fowler, who's been out since June 26 with an intercostal strain, will return to the Astros' starting lineup Wednesday afternoon against the Twins after completing his Minor League rehab assignment, the team said Tuesday.

Fowler played four rehab games at Triple-A Oklahoma City without any medical issues, going 3-for-10. In his first season with the Astros, he was batting .270 with a .377 on-base percentage and six homers and 24 RBIs in 76 games, so his offense was certainly missed.

He joins the lineup just as the team found out rookie outfielder George Springer would be out for another two weeks as he continues to rehab a quad strain.

"Dexter had no issues at all in his rehab, so he'll be ready to go," general manager Jeff Luhnow said. "We'll need him. He's a missed part of our lineup, as well, and without those two guys, quite frankly, it's a different team. We need them both, and we'll take what we can get right now, which is one of those guys now and another in a couple of weeks."

Astros manager Bo Porter said Jake Marisnick, who's been playing center since coming over in a trade from the Marlins two weeks ago, would slide over to right to accommodate Fowler.

"I thought Dexter and George would be back at the same time, if not one right behind the other," Porter said. "With George being set back, Marisnick will move to right field, just looking at the configuration of our ballpark. We'll see what we'll do in left field."

Expect Robbie Grossman, who hit .250 with a .396 on-base percentage in his first 28 games since being recalled July 8, to get most of the playing time in left.

"Robbie Grossman has done a good job," Porter said. "He's swinging the bat well, he's taking his walks. He looks more aggressive at balls early in the strike zone. We will continue to give him opportunity as well."

Porter pleased to see Santana own up to mistake

HOUSTON -- Astros rookie outfielder Domingo Santana's teammates and manager rushed to his defense Tuesday after he made an inexplicable mental mistake in the ninth inning of Monday's 4-2 loss to the Twins that led to a run.

Santana, who was optioned to Triple-A Oklahoma City after Tuesday's 10-4 win to open a roster spot for outfielder Dexter Fowler, went 0-for-4 with three strikeouts Monday. He was 0-for-17 with 14 strikeouts in his limited time in the Major Leagues. But it was his mental gaffe in field that stood out.

With Jordan Schafer at second base and Brian Dozier at first and two outs in a tie game, Joe Mauer shot a single to left field that scored Schafer easily. Santana held onto the ball as Dozier raced all the way home with the second run, saying later he "panicked."

"You turn on the TV and watch SportsCenter and I'm pretty sure he knows it's not something you should do on the baseball field," manager Bo Porter said. "Tarrick Brock, our outfield coach, talked to him and his teammates talked to him. I will be the fatherly figure that will put my arm around him and take care of his emotional side. It's obvious to everyone that's not something that should have happened. We will address it and let it be a teachable moment and move forward."

Astros second baseman Jose Altuve talked to Santana in the dugout moments after the play and tried to let him know mental mistakes are part of the game.

"He was a little worried," Altuve said. "But I told him that's happened before. We've all made mistakes before, so that won't be the last one you're going to make. Just go out and come back and play hard tomorrow."

Altuve admitted there was some confusion in terms of who should to take the relay throw at second because he was lined up in shallow right field during a defensive shift for Mauer, and shortstop Gregorio Petit had dived for the ball and was briefly out of position.

"He didn't have anybody to throw the ball to," Altuve said. "I wasn't on second base."

Porter said he appreciated the way Santana took ownership of the mistake.

"What I really like about it is the young man was flat-out honest," he said. "He said, 'I panicked.' For him to have the courage to stand there and say that, it speaks more value to me about his makeup. That's why you look at his struggles and believe he's going to come out on the other side of it. When you can stand up and admit it like he admitted [Monday] night, it's a huge step in the right direction in my book."

Castro poised to complete first healthy season

HOUSTON -- Astros catcher Jason Castro is on his way toward his first full healthy season in the Major Leagues. The fact he had a heat pack on his neck and back before Tuesday's game was just part of late-season maintenance.

"I'm just trying to stay loose," he said. "I think I slept a little weird [Monday] night and the neck is a little stiff."

Castro entered Tuesday having played 95 games, which is 25 shy of his career-high 120 a year ago. He also had 359 at-bats, which means he should surpass the career-best 435 at-bats in 2013, a season in which he missed the final two weeks after having a cyst on right knee drained.

Castro, of course, missed the entire 2011 season following a devastating knee injury suffered in Spring Training that year, and he battled knee and foot injuries in '12.

"I've been pretty happy with it," he said. "I've been feeling physically pretty good. I've been thankful and lucky for that, and I just keep getting my work in so I can finish the season healthy and as strong as I can."

Castro has started at catcher in 82 of the Astros' games this year and also has made 11 starts at designated hitter.

Brian McTaggart is a reporter for MLB.com and writes an MLBlog, Tag's Lines. Follow @brianmctaggart on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.