ARLINGTON -- Astros general manager Jeff Luhnow on Monday refused to address reports No. 1 overall pick Brady Aiken remains unsigned because of an issue with his elbow ligament that was revealed in a physical and said he remains hopeful the club can sign him and fifth-round pick Jacob Nix prior to the July 18 deadline.

Aiken, a left-handed pitcher from Cathedral Catholic High School in the San Diego area, came to Houston two weeks ago to sign after reaching a deal on a $6.5 million signing bonus, but left with his family two days later with neither he nor the team commenting.

The Astros, who never confirmed they had reached an agreement with Aiken, are now trying to sign the 17-year-old for $5 million, CBSSports.com reported Monday. The slot value for the No. 1 pick this year is $7,922,100.

"We're still working to get both unsigned players signed. As of now, we have no agreement with either player," Luhnow said. "We've got until the 18th [of July] and we're going to keep working with the goal of getting them both signed, and there's a couple of other later in the Draft as well. Those are two, the first and the fifth [rounders]."

If the Astros don't sign Aiken prior to July 18, they would receive pick 1a in next year's Draft, so essentially the No. 2 overall pick, as compensation. That's assuming they offer 40 percent of the assigned slot value.

"It's happened in a couple of cases but never this high," said Luhnow, who has been negotiating directly with the Aiken family.

Nix, a 6-foot-3 right-handed pitcher from Los Alamitos High School in California, told MLB.com three weeks ago he had reached an agreement on a signing bonus, but Luhnow hinted his signing is contingent on the Aiken signing. Aiken and Nix both have college commitments to UCLA.

"We like to sequence them in a way that makes sense," he said. "That's why even one maybe, possibly could have gotten done earlier, it hasn't gotten done because it depends on the other."

Luhnow said considering both Aiken and Nix were high school seniors, he's not worried about them losing developmental time.

"We're concerned about giving them a professional baseball experience and that could be accomplished with 20, 30 innings in the month of August," he said.

Unlike NFL players, who are subject to detailed physical exams during the league's annual combine, amateur baseball players aren't subject to physicals until an agreement is reached, though the team can do as much homework as possible in requesting medical files and performing psychological evaluations.

Luhnow said scouting directors pushed a few years back for more medical due diligence on players they were drafting, but it's a challenge logistically.

Aiken arrived in Houston on June 23 with his parents, Linda and Jim Aiken, and his sister, Halle, who plays volleyball at San Diego State, eager to get a deal done. Brady was scheduled to take a physical in Houston before signing.

"We're very, very excited to be here," Jim Aiken told MLB.com then. "[Tuesday] is a big day for us. We're really looking forward to it."

Aiken posted a 7-0 record and a 1.06 ERA in 11 starts in his senior season. He was a 2014 Perfect Game first team All-American and an All-Region first team in California. He led Team USA to the gold medal at the 18-and-under World Cup in Taiwan last September by winning both of his starts -- including a championship-game performance against Japan in which he struck out 10 and allowed one run over seven innings.

"I know all the fans and everyone are looking forward to this and I'm looking forward to this just as much as they are," Brady Aiken said upon arriving in Houston. "I'm more excited than they are probably to be honest with you. I'm really excited to see what the future holds."