The Houston Astros have until Friday to sign first overall pick Brady Aiken to a contract.

Casey Close, the high school left-hander's advisor, has criticized the team for using medical concerns to pressure Aiken into agreeing to a lesser bonus.

"We are extremely disappointed that Major League Baseball is allowing the Astros to conduct business in this manner with a complete disregard for the rules governing the draft and the 29 other clubs who have followed those same rules," Close said.

Houston reportedly has a $6.5 million agreement with Aiken.

"Throughout this process, we have been in touch with MLB to ensure that we are adhering to the rules at every point and we are confident that this has been the case," Jeff Luhnow said.

The Astros believe that Aiken's physical revealed a "significant abnormality" in the area of his elbow ligament, according to major-league sources.