Evidence suggests Michael Crabtree suffered a calf injury and could rejoin his San Francisco 49ers teammates for practice Thursday afternoon.

The 49ers have disclosed no details because doing so would ... compromise national security, right?

Teams and players do sometime have good reasons for withholding specifics on injuries. More on those in a bit.

For a player such as Crabtree, the lack of disclosure comes at a price. We're left to wonder about the severity of the injury. How badly is Crabtree hurt? Is he looking to extend his streak of missed exhibition games? He's never participated in one, a sore point in the past.

Rules require teams to disclose injuries beginning the week before the opening of the regular season. At that point, teams must disclose information for any player missing any of the 11-on-11 team portion of practice or individual drills.

The NFL's media policy for 2012 spells out requirements for injury reports:

"Clubs must ensure that all medical information issued to the media is credible, responsible, and specific in terms that are meaningful to teams, media, and fans. This includes the information in the weekly injury reports and the information on injuries announced to the media during games. "As a reminder, please note that because the injury reporting policy relates directly to the integrity of the game, compliance with the policy is a subject governed by the annual certifications required under the 'Integrity of the Game' initiative. These certifications are required from owners, club presidents, general managers and head coaches. "Club management, in consultation with its medical staff, is responsible for the accuracy and appropriateness of medical information that is distributed in response to public interest. Also in response to public interest, Super Bowl competing teams are required to submit injury report information during the week between the Championship Games and Super Bowl."

The 49ers are in compliance with the rules at this stage of the offseason. Once the league requires injury reports, there's little incentive for teams to supply more than the minimum information required under the policy.

Players often fear opponents will target injuries if too much is known. A quarterback with bruised ribs comes to mind as one example. If he misses practice, the team must disclose the injury. If he does not miss practice, the team would be smart to keep the injury information from opponents.

At this stage of the offseason, teams could seemingly compromise little if they offered general information. Will the player most likely return in a few days? Is the injury more serious? Absent such concessions, the summer guessing games will continue.