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9/6/2013 3:10 A.M. ET

Dominguez out with sinus infection

OAKLAND -- The illness that has kept Matt Dominguez out of the Astros lineup the past three days has been deemed a sinus infection, the third baseman said before Thursday's contest against the Astros.

Dominguez said he first began feeling the symptoms during Monday's game against the Twins.

"They gave me some medicine and I feel a lot better," Dominguez said. "I didn't really know what it was. I had never had one before. I got very light-headed and dizzy for no reason. When I looked around I had a lot of pressure in my head."

Astros manager Bo Porter said they're shooting for Dominguez to return to the lineup in some capacity on Friday.

"He's just not back at full strength," Porter said. "They gave him an I.V. yesterday. It's just one of those things that has to take its course. The training staff is doing everything it can to just try and get his energy level up, and hopefully by tomorrow he should be at least well enough to be able to give it a go."

Porter ejected during victory vs. Athletics

OAKLAND -- Astros manager Bo Porter was ejected in the eighth inning of Houston's 3-2 win against the A's on Thursday after arguing a call with home-plate umpire Mark Ripperger.

Porter approached Ripperger after A's catcher Stephen Vogt was called safe at home on a fielder's choice flip attempt by reliever Jorge De Leon to catcher Matt Pagnozzi to tag Vogt out and end the inning.

"When you slow it down, it looked like the guy probably was safe," Porter said. "But in my opinion, at that point in the game, the ball being there and from the way I saw it from the dugout, it looked like he was clearly out. Obviously, if you have the benefit of replay you can slow it down frame-by-frame, you may see it a little different. But at that point I have to defend my team."

The ejection was Porter's second of the season.

"It's the high-intensity of the game," Porter added. "It's how hard these guys are working. To have a play be that bang-bang, that close and you feel like, obviously, with the naked eye that guy's out. I mean, at that point I'm going to do everything I have to do to defend our team."

Grossman not rushing back from oblique strain

OAKLAND -- Astros outfielder Robbie Grossman remains day to day as he continues to recover from a strained oblique sustained while swinging the bat in the 12th inning of Tuesday's game against the Twins.

He's received ice and muscle stimulation treatments, but it still feels sore and tender.

"Obliques are strange," Astros manager Bo Porter said. "It's not something that you can put a timetable on and say he'll be ready tomorrow. I think it all depends on the progression and the pain tolerance as well. But he's better today than he was yesterday, which is promising."

Porter has relied on recent callups Marc Krauss and Trevor Crowe, who started Thursday as the team's designated hitter and left fielder, respectively, to help fill voids in a roster with multiple injuries.

"Trevor Crowe was playing extremely well before he injured his shoulder," Porter said. "It was unfortunate that we lost him for the period of time in which we lost him because he had started swinging the bat well, he was playing great defense, he was able to get himself healthy, he went back to Oklahoma City and played well and he's pretty much picked up where he left off before the injury.

"Krauss, who had been here, went back down to Oklahoma City. He was playing well there. So it was good to have those guys back here, especially at a time where we started to lose a few of our regular guys."

Castro takes BP, nears return to starting lineup

OAKLAND -- All-Star catcher Jason Castro took batting practice before Thursday's series opener against the A's for the first time since leaving Monday's contest against the Twins with a sprained right knee and could be available to pinch-hit.

The Astros backstop had the knee drained on Tuesday. That alleviated the cyst he attained after fouling a ball off his knee in the first inning of Monday's game against Minnesota.

"I'm pretty happy with the kind of way it's gone on," said Castro, a two-time American League Player of the Week who's hitting .282 with 18 home runs and 56 RBIs this season. "I don't see why I can't get back in action shortly. We'll see depending on how BP goes today and we'll kind of go from there."

Astros manager Bo Porter has said he'd prefer easing Castro back into some at-bats before he inserts him back behind the plate.

"He very well could be available to hit later in the game," Porter said. "But we wanted him to at least go through a complete day and hopefully tomorrow he can get back in there."

Worth noting

• The start of the NFL season began Thursday night in Denver, and with it, the Astros' fantasy football league.

Manager Bo Porter seemed confident in his fantasy team's chances to win it all in the dugout before Thursday's contest against the A's after knocking other members of the league, commissioned by Brett Wallace.

"From the time we've had our draft, we've had 67 transactions and eight trades," Porter said. "I'm trying to figure out why we even had a draft.

"We had guys draft a player, release him before he even played a snap, and come back only a week later to pick the same player up."

Jeff Kirshman is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.