Brady Aiken, the No. 1 overall draft choice, and the Astros are in a high-stakes “game of chicken” in their negotiations, according to a person familiar with the talks, leading up to Friday’s deadline to sign amateur players.

Aiken, the prep lefty phenom, seeks to keep the $6.5 million original agreement with Houston, and his backers say he is healthy and sound; at least as of late Tuesday, he hadn’t dropped his price. Meanwhile, the Astros have been seeking a deep discount following a team medical exam that uncovered what the team seems to believe is a worrisome abnormality related to the ulnar collateral ligament in his left pitching elbow.

Some people familiar with the talks still believe the sides will work it out, at some compromise number, somewhere between the $6.5 million figure and the $3.17 million offer the Astros needed to make to retain his rights and prevent the 17-year-old lefty from becoming a free agent. And that makes sense. Both sides have too much to lose not to try to resolves this.

Aiken, a supreme talent, needs to play ball. And the second-division Astros can ill afford to lose Aiken -- and thanks to a quirk in the rule, perhaps two more prime draftees, as well.

While there’s been mostly acrimony lately, the reality is that if Aiken goes unsigned, he will become only the third No. 1 overall pick in MLB history not to sign. Amateurs with his type of talent and future generally do not pass up pro ball.

The issue remains the medical exam and how much, if any, to discount a deal for what the Astros believe to be an abnormality that carries increased risk, even beyond the obvious risk of drafting of a high school pitcher No. 1 in the first place. The perceived issue with the elbow ligament was first reported by CBSSports.com.

Sources say the Astros’ medical exam findings suggest the ligament to be very small, small enough to raise the question of whether it could eventually fall apart, as Evan Drellich of the Houston Chronicle reported. Meanwhile, Aiken’s backers say he’s been examined independently by the foremost doctors in the country, who they say find nothing to suggest there’s anything  concerning about Aiken’s elbow, certainly nothing that would make him worth less than the $6.5 million original agreement. They also point out he hit 97 mph in his final game in high school near San Diego and continues to pitch pain-free and impressively on his own.

Aiken’s backers also suggest the Astros are trying to take advantage of something that is really nothing. When he signs, one Aiken supporter points out, "They’re not sending him to the disabled list, they’re sending him to the Gulf Coast League."

Aiken’s people further note that he's asymptomatic. And Astros supporters point out that of course he is, otherwise he wouldn’t have been first; that no irregularity was picked up until the team’s medical exam.

Things are getting downright ugly as the deadline approaches, with Aiken’s adviser Casey Close telling FOXsports.com it’s “extremely disappointing” that MLB is allowing the Astros to act “with complete disregard to the rules governing the draft.”

Meanwhile, union leaders are lining up strongly behind Close. “It’s disappointing on a number of fronts with all that’s happened with respect to the draft process,” union leader Tony Clark said. “You can rest assured the manipulation we think happened is going to lead us to have a conversation.”

Astros GM Jeff Luhnow defended his team’s actions, saying by text, “Of course we are acting appropriately and within the rules. I won’t comment on unsigned players and we can’t comment on health issues so there is not much I can say If other parties want to portray the Astros in a negative light that is their choice, but we have acted properly at every turn."

And Dan Halem, MLB senior VP, backed up Luhnow. Halem said at the All-Star luncheon where MLB commissioner Bud Selig and Clark both spoke, “We believe the Astros have conducted themselves appropriately."

Especially troublesome to the union is that the Aiken case appears to be affecting another draftee, pitcher Jacob Nix, who had agreed to a $1.5-million bonus of his own that is now in limbo, as it seems to be tied to the Aiken situation. The Astros at least temporarily are said to have had to pull the offer to Nix, who passed his physical, as it seems they wouldn’t have the slot money with which to sign Nix unless an Aiken deal gets done.

In the somewhat complicated system, if Aiken goes unsigned, the Astros lose the entire $7.9 million in slot money attached to the No. 1 pick, and thus their ability to sign Nix, who seems to be an innocent bystander. (Luhnow declined comment on the Nix case, too, again citing his policy not to comment on “unsigned players.”)

Union leaders believe Aiken was done wrong, with the theory that the Astros are seeking an even  lower price on Aiken so they can afford No. 21 pick, lefthander Mac Marshall, who’s reported to also require $1.5 million. The Astros meanwhile simply view it as a case of seeing the player’s value drop after something came up in the medical, as has happened on rare occasions in previous drafts -- like when R.A. Dickey was discovered to have no ulnar collateral ligament and his bonus was dropped from $810,000 to $75,000. (That story obviously has a happy ending as Dickey a decade later re-invented himself as knuckleballer, won a Cy Young and signed a deal for almost $30 million).

While the Aiken staredown continues, it’s questionable whether either side can afford to pass.

The Astros, qualifiers to make the No. 1 pick three years running, can ill afford to lose a No. 1 talent. Sources suggest that he was easily their top pick, irrespective of price, for months. As Luhnow told CBSSports.com a few weeks ago, the failure to sign Aiken “would not be a good result."

Complicating matters is that a failure to sign Aiken also would mean a failure to sign Nix, a right-hander who’s a friend of Aiken’s and is also committed to UCLA, as well as Marshall. In the slotting system, the Astros were hoping to sign all three players, but the failure to sign Aiken could cause them to sign none of the three.

One more thing Nix and Aiken share is the same adviser, Close, and Close could lose both deals if Aiken and the Astros can’t come together. Aiken was said by everyone around the Astros to be anxious to get on with his professional career. His parents and sister were said to have been in Houston when the first offer was pulled off the table following the team’s medical exam.

It’s been a waiting game ever since, one neither side can afford to lose.