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6/29/2013 1:53 A.M. ET

Astros gearing up for international signing period

HOUSTON -- With most of the Astros' top Draft picks in the fold, general manager Jeff Luhnow said Friday the team's main focus now is the start of the July 2 international signing period. He said director of international Oz Ocampo is entrenched in the Dominican Republic in anticipation.

"From Monday at midnight and Tuesday night at midnight, there will be about $20-30 million spent by the industry in that one day," Luhnow said. "It's basically a free-for-all."

The Astros have the most money to spend, with a pool of $4.9 million, and there are penalties for teams that go over the pool. What makes the period even more intriguing is teams can trade cap space in exchange for players.

According to the Collective Bargaining Agreement, a 16-year-old international player can sign during the period that extends from July 2 through June 15 of the following year if the prospect turns 17 before Sept. 1 or by the completion of his first Minor League season.

Additionally, any prospect who is already 17 or older and has not previously signed a Major or Minor League contract, resides outside the United States, Canada and Puerto Rico and has not been enrolled in a high school or college in the U.S., Canada or Puerto Rico within the previous year is eligible to sign during the period.

"It's going to be like a dream come true for those guys," said Astros second baseman Jose Altuve, who signed at 16 out of Venezuela. "I know how excited I was to sign with the Astros, and those guys are feeling the same right now."

Altuve pushing for Castro's All-Star nod

HOUSTON -- Jose Altuve, who represented the Astros last year for the National League in the All-Star Game, said he believes catcher Jason Castro should be part of the American League squad during this year's Midsummer Classic.

Castro continued his solid season on Friday, belting his 11th home run while adding a walk.

"I'm sure he's going to make it," Altuve said. "He's having an All-Star year, and he's one of the guys that's been consistent all year long. We're almost halfway through the season right now and he's proven himself. He deserves to be there."

The players received their All-Star ballots on Friday. They're allowed to vote for one player at all nine positions, as well as eight pitchers (five starters and three relievers).

In addition to Altuve and Castro, starter Bud Norris could also warrant some All-Star consideration, but manager Bo Porter said he's not going to call AL manager Jim Leyland of Detroit to lobby for any of his guys.

"I'll let Leyland and his staff make the determination what they deem best for the AL team," he said. "I do think we have guys that are deserving, and it's one of those things from a standpoint of the overall selection and who they decide to select, I will respect whatever decision Jim Leyland and his staff makes."

Maxwell available off bench in opener

HOUSTON -- Astros outfielder Justin Maxwell, who was diagnosed with a mild concussion after his face hit the ground while diving for a ball on Tuesday, was cleared to play by doctors on Friday, but manager Bo Porter gave him an extra day, which is his practice.

Maxwell said he passed the impact test Thursday, the same test he failed on Wednesday. The test compares the players' ability to recognize and recall words and shapes based on a baseline test they took during Spring Training.

"It's pretty tedious," Maxwell said. "You have to sit in front of the computer and do a bunch of word recollections. It shows you a list of 20 words, and it shows you them twice and you have to recall which words were on the list and which were not. There's a bunch of shapes like arrows and circles, and you have to say whether or not you saw it previously.

"There's some other tasks in there, and at the end you recall the first group of words again and other shapes. I passed."

Porter likes to give players an extra day off when they're cleared to play following an injury.

"Especially when you're talking about a head injury," he said. "He passed all the tests and is available tonight if the game situation dictates. I'd rather give him a day to come out and run around and take batting practice and make sure everything is OK."

Astros sign ninth-round Draft pick Holberton

HOUSTON -- The Astros on Friday signed ninth-round pick Brian Holberton, a catcher from the University of North Carolina, leaving third-round pick Kent Emanuel, a left-handed pitcher who's also from North Carolina, as the club's only unsigned pick from among the top 10 rounds.

Holberton, who has been assigned initially to Rookie-level Greeneville, hit .308 with 54 runs, 12 home runs and 58 RBIs with a .419 on-base percentage and a .504 slugging percentage while helping the Tar Heels reach the College World Series.

"Brian brings a lot to our organization," scouting director Mike Elias said. "He hits for average and power and has shown us a professional approach throughout his career. He was a key figure in UNC's dominant offense this spring and helped lead them to the College World Series on both sides of the ball and in the clubhouse. He's a tireless worker, and his emergence as a catcher is something we're very excited about."

The club also announced the signing of left-hander Chris Cotton (14th round), third baseman Adam Nelubowich (18th round), catcher Jake Rodriguez (19th round) and right-hander Juan Santos (39th round). Cotton, Nelubowich and Rodriguez have been assigned to short-season Class A Tri-City while Santos will report to the Gulf Coast League.

The Astros have signed 29 of their 40 Draft picks this year.

Houston had the biggest Draft pool from which to spend money this year, and general manager Jeff Luhnow said the club can still go over slot to sign some high school players it took beyond the 10th round.

"You have a feel for your pool amount, but we have some high school players past the 10th round that to sign them will require using some of that pool," he said. "We still have a lot more variables out there."

Worth noting

• Right-handed pitcher Mark Appel, taken with the No. 1 overall pick out of Stanford earlier this month, threw a bullpen session earlier this week in Kissimmee, Fla., and looked good, Luhnow said. He's expected to remain in Florida a couple of more weeks before reporting to Tri-City.

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.