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8/28/2013 8:55 P.M. ET

Dominguez hits cleanup for first time this year

CHICAGO -- Astros third baseman Matt Dominguez celebrated his 24th birthday Wednesday by batting in the fourth spot in the lineup for the first time this season. All-Star catcher Jason Castro, who has been hitting fourth, was out of the lineup against Chris Sale, who's tough on lefties.

Dominguez hit fourth twice last year. He was moved into the fifth spot in the order earlier this week after batting eighth for much of the season. He entered Wednesday hitting .240 with 19 homers and 66 RBIs, including .340 (18-for-53) with five homers and 10 RBIs in his last 14 games.

"My swing feels good," Dominguez said. "I've got some good confidence going right now and going through a good little streak now, and the whole team is swinging it good and we're kind of feeding off each other."

Astros hitting coach John Mallee, who had Dominguez when he was drafted by the Marlins at 17 years old, said he's been working on slowing down his front side and staying behind the ball.

"He's always had the ability as a hitter," Mallee said. "He had some mechanical things to work on. Like any young hitter, his approach is going to get better and better and better the more he plays and he learns how to attack certain types of pitchers and how certain guys are trying to get him out. He's able to make adjustments more efficiently, and that's through experience."

Astros affiliates having banner seasons

CHICAGO -- The improvements the Astros have made in recent years in terms of adding talent to their Minor League system has been evident on the field. Oklahoma City, the Astros' Triple-A affiliate, clinched the Pacific Coast League Southern Division title on Tuesday with a win over Nashville.

The RedHawks join Double-A Corpus Christi, Class A Lancaster and Class A Quad Cities as Astros affiliates that have clinched playoff berths. What's more, short-season Tri-City and rookie league Greeneville are currently in first place, meaning the Astros could have six playoff clubs.

"It's an incredible step forward for the organization," Astros director of player development Quinton McCracken said. "First and foremost, it's a testament to the players themselves. Then you have to go to the coaches and the front office for accumulating the talent, starting with [former general manager] Ed Wade and some of the shrewd moves they made in the years prior, and then [current GM] Jeff Luhnow and the new front office and scouts for acquiring and developing talent.

"Kudos go the players for buying into the system, buying into our developmental plans for each and every one of them, and going out and working hard to get better on a daily basis. They're playing good, sound fundamental baseball, and we're seeing good results while we're developing players."

The Astros' combined Minor League record of 458-340 (.574) entering Wednesday was tops in baseball. Last year, the Astros had the top combined winning percentage among domestic Minor League clubs after being last overall in both 2010 and '11.

Oklahoma City will play the winner of the American Northern Division in a best-of-five series, starting Sept. 4-5 at Chickasaw Bricktown Ballpark in Oklahoma City.

Astros confident Altuve will snap out of slump

CHICAGO -- Astros second baseman Jose Altuve entered Wednesday in a 6-for-37 slump (.162) during which he had only two RBIs, dropping his batting average to .271. Manager Bo Porter and hitting coach John Mallee both believe he's due to break out of his funk.

"The biggest thing with Altuve right now is he's always been an aggressive, attack kind of hitter, and he needs to realize the league knows that he can hit, too," Porter said. "When they know that you can hit, they're not just going to lay the ball in the strike zone.

"I think he's just chasing a lot of pitches, and if he starts to take those pitches there's two things that are going to happen: One, he's going to start to walk more, and two: He's going to bring them back to the plate in which he's going to start getting the number of hits he would normally get."

Altuve remains a fixture at the third spot in the batting order. He batted .330 in April, .265 in May, .275 in June, .258 in July and .213 in August prior to Wednesday. Altuve has only drawn 28 walks in 535 plate appearances this year.

"Like any young player, he starts to press because he wants to do so good and when he's not having the success he's having sometimes it's a confidence issue," Mallee said. "I think he's going to snap out of it, and I know the manager is very supportive of him and continues to hit him in the meat part of the lineup. At the end of the day, he's one of the best hitters and I think he will be in the end."

Clemens happy with first start, but yearns to get better

CHICAGO -- Astros pitcher Paul Clemens, who wasn't too eager to speak with reporters at length following his first Major League start Tuesday, opened up a little bit more pregame on Wednesday. Clemens went six innings and held the White Sox to one run and four hits en route to a no-decision.

"Any time you give your team a chance to win, you're happy," Clemens said. "I'm a long way from where I want to be as far as a starting pitcher in this game. I gave my team a chance, but there were a lot of things I have got to do better throughout this ballgame."

Clemens pitched in 30 games in the bullpen earlier this year and didn't fare so well, posting a 6.36 ERA before being sent down to Triple-A Oklahoma City. He worked on improving his fastball command and will remain in the rotation the rest of the year as the Astros get a good look at what he can do as a starter.

"Any time you get an opportunity in the Major Leagues, it's an honor and privilege and you have to make the most of it no matter who you are or what your role is -- bullpen, starter, position players," Clemens said.

Astros hold annual in-season MLBPA meeting

CHICAGO -- Astros players held their annual in-season meeting with representatives from the Major League Baseball Players Association on Wednesday morning at the team hotel. Tony Clark, the MLBPA's deputy executive director, led the meeting.

All-Star catcher Jason Castro, who's the Astros' player representative to the union, said it was a "state-of-the-union" meeting and similar to the meeting the Astros have with the MLBPA during Spring Training each year.

"Just kind of got some of the newer guys a better idea of what it is they really do on a daily basis with some of the topics going on right now and where we're headed and some topics that could be coming up in the offseason and things like that," Castro said. "Just kind of an introduction of the staff to a lot of the guys who haven't had a chance to meet them yet."

The hot-button issues should be no surprise: The proposed expansion of instant replay and the fallout from the Biogenesis suspensions levied earlier this month.

"We wanted to make sure what we have ahead of us and trying to make sure everyone is on the same page and has the same information," Castro said. "That's really one thing we try to pride ourselves on is the union is only as strong as every member. We try to do everything we can to keep everyone informed and on the same page and pulling in the same direction."

Castro said he's in the process of trying to find a couple of players to fill the role of alternate reps to the union, but he said several players have expressed interest in stepping up. Those roles were filled by Justin Maxwell and Carlos Pena, both of whom are with the Royals.

Worth noting

• Outfielder George Springer and pitcher David Martinez were named Texas League Player and Pitcher of the Year, respectively, for what they did at Double-A Corpus Christi prior to their promotions to Triple-A Oklahoma City. They were joined in the Texas League post-season All-Star team by pitcher Mike Foltynewicz, third baseman Jonathan Meyer and catcher Max Stassi.

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.