To have a valid trademark, one must use the mark "in commerce." Using a mark in commerce means to use the mark in the ordinary course of trade, not merely to reserve a right in the mark. In lieu of actual use, one can file an intent-to-use application, which gives the applicant six to 24 months from the date of the application to use the mark in commerce.
This poses an unique problem for NCAA athletes. For example, Johnny Manziel won the Heisman Trophy in 2012. He has an especially catchy nickname, "Johnny Football." The NCAA has allowed him to protect his rights while competing for Texas A&M University, but he cannot exploit the use of the name "Johnny Football" as a trademark. To do so would require that he use the mark "in commerce," which by definition would render him ineligible to compete in college football.
On November 1, 2012, Manziel's representatives filed an intent-to-use application with the U.S. Patent and Trademark Office. This gave him six months to file allegation of use -- that the mark is being used in commerce -- or to file for an extension of the six month period. If there is "good cause," an intent-to-use applicant can be given 24 months from the initial application during which they must use the mark in commerce to reserve rights in the mark. "Good cause" would surely be granted in cases where the applicant cannot use the mark in commerce due to NCAA rules.
In connection with a lawsuit filed by Manziel against an alleged infringer, Manziel filed a trademark application on February 2, 2013. This application alleged use of the mark in commerce, which requires that he use his nickname in connection with goods for monetary gain. Under Texas law, Manziel might have a stronger argument. States have trademark law that supplements U.S. trademark law. However, I know of no state's trademark law that allows for the reservation of trademark rights without using the mark "in commerce."
The best way for Manziel to get around the issue would have been to file the intent-to-use application, and file the maximum number of extensions so he would have 24 months from the initial application to use the mark in commerce. The 24 month period would have expired on November 1, 2014, during his redshirt junior season. By that time he would be eligible for the NFL Draft. (Football players are required to wait three years from their last high school season before they can declare for the NFL Draft.)
Manziel stands a very low chance of winning any trademark infringement cases before the "Johnny Football" mark can be registered on the Principal Register. One must have ownership rights in a trademark before they can file suit to enforce those rights. It is an unfortunate situation, because it indicates a genuine conflict between U.S. trademark law and NCAA rules. It may only get worse, because collegiate sports figures are more prominent now than they ever have been. In recent years, college sports have exploded in popularity, and people that used to only be known among college sports fans are now household names: RG3, Tim Tebow, etc.