HOUSTON -- The Astros have narrowed the field in their "You Make The Call" radio apprentice contest to four finalists: Jake Atkinson of Spring, Texas; Alex Del Barrio of Mission, Texas; Crawford Jones of Houston; and Nate Kurant of Kenneth City, Fla.

The final four contestants will each broadcast a segment of the Astros' radio broadcast during one of the next four games -- Kurant on Thursday, Atkinson on Friday, Del Barrio on Saturday and Jones on Sunday.

Fans will once again have the opportunity to vote on the on-air performances online at Astros.com between Sept. 5-10, with the final two contestants being announced Sept. 12.

The final round of the competition will consist of the two finalists performing various duties during the Sept. 13-14 radio broadcasts. The Astros will announce the winner of the contest during the pregame ceremony of the final home game of the season Sept. 26.

The winner will have the opportunity to work as part of the 2013 radio broadcast team in a role that will include conducting pre- and post-game interviews, covering press conferences and serving as a roving reporter during games. This new role does not include calling games.

The Astros received online entries from more than 300 people from 17 different states after announcing the competition in July. The four remaining contestants were selected by a combination of fan votes and voting by two judges: former Astros pitcher, manager and broadcaster Larry Dierker and broadcaster Linda Lorelle. More than 26,000 fan votes were received for the second round of the competition.

Astros calling up infielder Dominguez

HOUSTON -- The Astros are going to call up third baseman Matt Dominguez from Triple-A Oklahoma City in time for him to be in uniform for Thursday's series finale against the Giants.

Dominguez, acquired from the Marlins on July 4 in the Carlos Lee trade, is hitting .298 with two homers and 23 RBIs for the RedHawks. He appeared in four games for the Astros earlier this year and had two hits in eight at-bats.

Astros general manager Jeff Luhnow said a corresponding roster move will be announced Thursday. Houston outfielder Ben Francisco was scratched from the lineup just prior to Wednesday's game with what interim manager Tony DeFrancesco called a right wrist strain, but the extent of the injury isn't known.

Dominguez, the Marlins' 12th overall pick in the 2007 First-Year Player Draft, is regarded as a standout defensive player who has had his struggles at the plate. In 78 games with Triple-A New Orleans prior to getting traded, the 23-year-old batted .234 with seven home runs and 46 RBIs in 78 games.

Knee feeling good, Castro concentrating on baseball

HOUSTON -- Six weeks after having his surgically repaired right knee drained, Astros catcher Jason Castro isn't worrying about the stability of the knee. He's been able to just focus on baseball.

"It's been feeling really good, especially the past week or so," Castro said. "After I got through that first series back off the DL, it's actually felt probably the best it's felt all year."

Castro went on the disabled list July 8 with right knee effusion. He had the knee drained July 18 and returned to the lineup in Chicago on Aug. 13. In nine games since returning, Castro is batting .286 (8-for-28).

Castro and veteran catcher Chris Snyder have been alternating games at the position for the last week.

Over the final month of the season, Castro is looking to improve both behind the plate and at the plate. He wants to continue to build relationships with the Astros pitching staff, especially with the new guys.

The postseason may be out of reach, but Castro will cherish the remaining 33 games after missing the entire 2011 season with a torn ACL in the right knee.

"It's really important for me," Castro said. "Having missed all of last year, it's just getting as much playing time as I can."

Biggio gives Astros motivational speech

HOUSTON -- Astros interim manager Tony DeFrancesco had Craig Biggio address the team in a meeting prior to Wednesday's game, a speech that emphasized to the young team the right way to play the game, such as taking an extra base and always hustling.

"We're just trying to keep the place loose and motivated," DeFrancesco said. "I brought Biggio in to talk to the guys and we're trying to find out the Astros way, what it was like back in the era when they dominated and they got to the World Series. For me, there's no better person than the guy I knew since he was 21 years old."

DeFrancesco and Biggio both played baseball at Seton Hall University, but not together. DeFrancesco left the school to start his professional career in 1984 just as Biggio was arriving. Biggio jumped at the chance to talk to the team.

"I was honored to do it," Biggio said. "Obviously, this organization has been the only organization I've ever played with, and getting the opportunity to talk in front of the boys was a nice thing."

Biggio, who played 20 years for the Astros and has been associated with the club for 25 of its 50 years, broke into the Majors in 1988 and said he learned the right way to play the game from guys like Nolan Ryan, Buddy Bell and Bill Doran, who helped him make the transition to second base.

"You want to make sure the legacy is continued and you're playing the right way because that's the only way you're supposed to play the game," Biggio said.

Cosart, Singleton among Astros' AFL players

HOUSTON -- Several of the Astros' top prospects, including pitcher Jarred Cosart, first baseman Jonathan Singleton and center fielder George Springer, are among the seven players the club will send to participate in the Arizona Fall League this season.

Also playing in Arizona will be pitchers Chia-Jen Lo and Alex Sogard and infielders Bobby Borchering and Jiovanni Mier, who will be on the taxi squad and activated only on Wednesdays and Sundays as he comes off an injury-filled 2012.

The Astros' contingent is assigned to the Mesa Solar Sox, which is managed by Rodney Linares, the skipper at Class A Lancaster. The season will begin Oct. 9 and end Nov. 17.

Each Major League organization is required to provide seven players. All Triple-A and Double-A players are eligible, provided they are on Double-A rosters no later than Aug. 15. Each organization is permitted to send two Class A Advanced-level players in addition to the current allowance of two "A exempt" players (who are under contract as of Aug. 15). Foreign players are allowed as long as the player is not on his native country's primary protected-player list.

No players with more than one year active or two years total of credited Major League service as of Aug. 31 (including Major League disabled-list time) are eligible, except a team may select one player picked in the most recently concluded Major League Rule 5 Draft.

Worth noting

• Astros pitcher Bud Norris, who left Tuesday's game with a blister on his right middle finger, is expected to make his next start, DeFrancesco said. Norris leads the team with 14 quality starts in 24 outings, but he hasn't won since May 21.

• DeFrancesco said Jimmy Paredes, who made his season debut with the Astros on Tuesday while getting his first career start in right field, will eventually get some time in left field later this season. The Astros want him to get more comfortable in the outfield before putting him in the tricky left field at Minute Maid Park.