The NCAA football rules committee is proposing changes for the 2014 season that would loosen the reins on defensive substitutions and lessen the penalties for targeting fouls called on the field.

The committee's proposal would allow defensive players to substitute within the first 10 seconds of the 40-second play clock, except for the final two minutes of each half.

The rules committee says they hope to enhance safety by guaranteeing a small window for both teams to substitute. UCF receiver Breshad Perriman is shown in November after a play for which Houston's Zach McMillian was called for targeting. Joshua Cruey/Orlando Sentinel/Getty Images

Offenses that snap the ball before 29 seconds remain on the play clock would receive a 5-yard delay-of-game penalty.

Current rules state that defensive players aren't guaranteed the opportunity to substitute unless the offense first substitutes. Under the proposal, this policy would remain when the play clock starts at 25 seconds.

The proposal would strike a major blow to up-tempo spread offenses that often run plays before the opposing defense is set. Coaches like Alabama's Nick Saban and Arkansas' Bret Bielema last summer said that up-tempo offenses are likelier to cause injuries for defensive players who can't get off of the field in time.

"This rules change is being made to enhance student-athlete safety by guaranteeing a small window for both teams to substitute," Air Force coach Troy Calhoun, chair of the rules committee, said in a prepared statement. "As the average number of plays per game has increased, this issue has been discussed with greater frequency by the committee in recent years and we felt like it was time to act in the interests of protecting our student-athletes."

The committee, which met this week in Indianapolis, believes 10 seconds of substitution time wouldn't inhibit offenses from operating quickly. It points to research that states that offenses rarely snap the ball before 30 seconds remain on the play clock.